图像处理------颜色梯度变化 (Color Gradient)

  - created by gloomyfish

有过UI设计经验的一定对2D图形渲染中的Color Gradient 或多或少有些接触，很多编程

语言也提供了Gradient的接口，但是想知道它是怎么实现的嘛？

 

本文介绍三种简单的颜色梯度变化算法，就可以很容易实现常见的梯度变化算法

三种都要求提供两个参数即起始颜色RGB值, 最终颜色RGB的值。

 

垂直梯度颜色变化，效果如下：

水平梯度颜色变化，效果如下：

水平与垂直两个方向叠加梯度变化效果如下：

r = endColor[0] + (int)(rr * ((float)row/255.0f) +0.5f);g = endColor[1] + (int)(gg * ((float)row/255.0f) +0.5f);b = endColor[2] + (int)(bb * ((float)row/255.0f) +0.5f);

算法代码及其解释

 

计算起始颜色和终点颜色RGB之间差值代码如下：

float rr = startColor[0] - endColor[0];float gg = startColor[1] - endColor[1];float bb = startColor[2] - endColor[2];

实现垂直梯度变化的代码如下：

r = endColor[0] + (int)(rr * ((float)row/255.0f) +0.5f);g = endColor[1] + (int)(gg * ((float)row/255.0f) +0.5f);b = endColor[2] + (int)(bb * ((float)row/255.0f) +0.5f);

实现水平梯度变化代码如下：

// set gradient color valuefor each pixelr = endColor[0] + (int)(rr * ((float)col/255.0f) +0.5f);g = endColor[1] + (int)(gg * ((float)col/255.0f) + 0.5f);b = endColor[2] + (int)(bb * ((float)col/255.0f) +0.5f);

实现水平和垂直两个方向上Gradient叠加代码如下：

r = endColor[0] + (int)(rr * (((float)col * (float)row)/size) +0.5f);g = endColor[1] + (int)(gg * (((float)col * (float)row)/size) +0.5f);b = endColor[2] + (int)(bb * (((float)col * (float)row)/size) +0.5f);

程序对上面三种Gradient方法分别放在三个不同的方法中，根据参数调用。

程序的完全Java源代码如下：

import java.awt.BorderLayout;  import java.awt.Dimension;  import java.awt.Graphics;  import java.awt.Graphics2D;  import java.awt.RenderingHints;  import java.awt.image.BufferedImage;    import javax.swing.JComponent;  import javax.swing.JFrame;    public class ColorGradientDemo extends JComponent {        /**      *       */      private static final long serialVersionUID = -4134440495899912869L;      private BufferedImage image = null;            protected void paintComponent(Graphics g) {          Graphics2D g2 = (Graphics2D)g;          g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);          g2.drawImage(getImage(4), 5, 5, image.getWidth(), image.getHeight(), null);      }            public BufferedImage getImage(int type) {          if(image == null) {              image = new BufferedImage(256, 256, BufferedImage.TYPE_INT_ARGB);              int[] rgbData = new int[256*256];              if(type == 1) {                  generateVGradientImage(rgbData);              } else if(type == 2) {                  generateHGradientImage(rgbData);              } else {                  generateHVGradientImage(rgbData);              }              setRGB(image, 0, 0, 256, 256, rgbData);          }          return image;      }        private void generateVGradientImage(int[] rgbData) {          int[] startColor = getStartColor();          int[] endColor = getEndColor();                    float rr = startColor[0] - endColor[0];          float gg = startColor[1] - endColor[1];          float bb = startColor[2] - endColor[2];                    int a=255;          int r=0, g=0, b=0;          int index = 0;          for(int row=0; row<256; row++) {              for(int col=0; col<256; col++) {                  // set random color value for each pixel                  // set gradient color value for each pixel                  r = endColor[0] + (int)(rr * ((float)row/255.0f) + 0.5f);                  g = endColor[1] + (int)(gg * ((float)row/255.0f) + 0.5f);                  b = endColor[2] + (int)(bb * ((float)row/255.0f) + 0.5f);                                    rgbData[index] = ((a & 0xff) << 24) |                                  ((r & 0xff) << 16)  |                                  ((g & 0xff) << 8)   |                                  ((b & 0xff));                  index++;              }          }      }            private void generateHGradientImage(int[] rgbData) {          int[] startColor = getStartColor();          int[] endColor = getEndColor();                    float rr = startColor[0] - endColor[0];          float gg = startColor[1] - endColor[1];          float bb = startColor[2] - endColor[2];                    int a=255;          int r=0, g=0, b=0;          int index = 0;          for(int row=0; row<256; row++) {              for(int col=0; col<256; col++) {                                    // set gradient color value for each pixel                  r = endColor[0] + (int)(rr * ((float)col/255.0f) + 0.5f);                  g = endColor[1] + (int)(gg * ((float)col/255.0f) + 0.5f);                  b = endColor[2] + (int)(bb * ((float)col/255.0f) + 0.5f);                                    rgbData[index] = ((a & 0xff) << 24) |                                  ((r & 0xff) << 16)  |                                  ((g & 0xff) << 8)   |                                  ((b & 0xff));                  index++;              }          }      }            private void generateHVGradientImage(int[] rgbData) {          int[] startColor = getStartColor();          int[] endColor = getEndColor();                    float rr = startColor[0] - endColor[0];          float gg = startColor[1] - endColor[1];          float bb = startColor[2] - endColor[2];                    int a=255;          int r=0, g=0, b=0;          int index = 0;          float size = (float)Math.pow(255.0d, 2.0);          for(int row=0; row<256; row++) {              for(int col=0; col<256; col++) {                  // set random color value for each pixel                  r = endColor[0] + (int)(rr * (((float)col * (float)row)/size) + 0.5f);                  g = endColor[1] + (int)(gg * (((float)col * (float)row)/size) + 0.5f);                  b = endColor[2] + (int)(bb * (((float)col * (float)row)/size) + 0.5f);                                    rgbData[index] = ((a & 0xff) << 24) |                                  ((r & 0xff) << 16)  |                                  ((g & 0xff) << 8)   |                                  ((b & 0xff));                  index++;              }          }      }            public int[] getStartColor() {          return new int[]{246,53,138};      }            public int[] getEndColor() {          return new int[]{0,255,255};      }            public void setRGB( BufferedImage image, int x, int y, int width, int height, int[] pixels ) {          int type = image.getType();          if ( type == BufferedImage.TYPE_INT_ARGB || type == BufferedImage.TYPE_INT_RGB )              image.getRaster().setDataElements( x, y, width, height, pixels );          else              image.setRGB( x, y, width, height, pixels, 0, width );      }            public static void main(String[] args) {          JFrame frame = new JFrame("Gradient Color Panel");          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);          frame.getContentPane().setLayout(new BorderLayout());                    // Display the window.          frame.getContentPane().add(new ColorGradientDemo(), BorderLayout.CENTER);          frame.setPreferredSize(new Dimension(280,305));          frame.pack();          frame.setVisible(true);      }    }