opencv中获取和编辑图像像素值

1. Access pixel value in Mat Image

For a single channel grey scale image (type 8UC1).

Scalar intensity = img.at<uchar>(Point(x, y));

For a 3 channel image with BGR color ordering (the default format returned by imread):

Vec3b intensity = img.at<Vec3b>(y, x);uchar blue = intensity.val[0];uchar green = intensity.val[1];uchar red = intensity.val[2];

The same method can be used to change pixel intensities:

img.at<uchar>(y, x) = 128;

2. How can I set all pixel values to a specific value?

http://stackoverflow.com/questions/20816955/how-to-set-all-pixels-of-an-opencv-mat-to-a-specific-value

• • For grayscale image:

    <code style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; white-space: inherit;"><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">cv</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">::</span><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Mat</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> m</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">100</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">100</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> CV_8UC1</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">);</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="com" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 128, 128); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">//gray </span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">m </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">=</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Scalar</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">5</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">);</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">  </span><span class="com" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 128, 128); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">//used only Scalar.val[0] </span></code>

    or

    <code style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; white-space: inherit;"><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">cv</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">::</span><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Mat</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> m</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">100</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">100</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> CV_8UC1</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">);</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="com" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 128, 128); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">//gray </span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">m</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">.</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">setTo</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Scalar</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">5</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">));</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">  </span><span class="com" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 128, 128); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">//used only Scalar.val[0] </span></code>

    or

    <code style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; white-space: inherit;"><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Mat</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> mat </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">=</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Mat</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">100</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">100</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> CV_8UC1</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> cv</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">::</span><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Scalar</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">5</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">));</span></code>

  • For colored image (e.g. 3 channels)

    <code style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; white-space: inherit;"><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">cv</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">::</span><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Mat</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> m</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">100</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">100</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> CV_8UC3</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">);</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="com" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 128, 128); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">//3-channel </span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">m </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">=</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Scalar</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">5</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">10</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">15</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">);</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">  </span><span class="com" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 128, 128); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">//Scalar.val[0-2] used </span></code>

    or

    <code style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; white-space: inherit;"><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">cv</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">::</span><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Mat</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> m</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">100</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">100</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> CV_8UC3</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">);</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="com" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 128, 128); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">//3-channel </span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">m</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">.</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">setTo</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Scalar</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">5</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">10</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">15</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">));</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">  </span><span class="com" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 128, 128); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">//Scalar.val[0-2] used </span></code>

    or

    <code style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; white-space: inherit;"><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Mat</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> mat </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">=</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Mat</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">100</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">100</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> CV_8UC3</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;"> cv</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">::</span><span class="typ" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(43, 145, 175); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">Scalar</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">(</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">5</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">10</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">,</span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; color: rgb(128, 0, 0); background-color: transparent; background-position: initial initial; background-repeat: initial initial;">15</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-size: 13.63636302948px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">));</span></code>

3. How to set pixel values for a block of pixels?

For a 3-channel color image: use Range() function

[cpp] view plaincopy

1. img(Range(0, 1), Range(0, 1)) = Scalar(128, 128, 128);  

4.  How to copy a block of Mat matrix to another matrix?

Do NOT Use Range() function again! 

[cpp] view plaincopy

1. Mat M = img(Range(10,10), Range(100,100)); // copy a rectangular part of Mat img to initialize a new Mat M.  
2.   
3. Mat M(Range(10,10), Range(100,100)) = img(Range(10,10), Range(100,100)); // change pixel values of part of Mat M using a block of img  

 The code above cannot work because Range() is just copying the header of the matrix. We should use copyTo() instead.

[cpp] view plaincopy

1. img.copyTo(M(Rect(10, 10, width, height)));  

Here, we should pay attention on usage of Rect. The first two input of Rect is the position of the left upper corner of ROI (Region of Interest). And the last two inputs are the width and height of ROI, not the position of right lower corner.