Use GIL

This article is a simple example about how to use GIL to generate histogram.

 

usually, a png file is managed as a image view of gil. also, a image view could be treated as 2D array. To generate histogram, we should just make a relation between the histogram element value and the pixel value.

 

In the following example, firstly generate a png file with a histogram, then read back to histogram from the generated png file.

 

// Find link the libs!#pragma comment( lib, "libpng.lib" )#pragma comment (lib, "libzlib.lib" ) #define png_infopp_NULL (png_infopp)NULL#define int_p_NULL (int*)NULL#include <boost/gil/extension/io/png_io.hpp>#include <boost/gil/image.hpp>#include <boost/gil/extension/io/png_dynamic_io.hpp>#include <boost/gil/typedefs.hpp>using namespace boost::gil;int main(){ // Histogram to generate image view. int HistGram[256][256] = { {0} ,{10} ,{30} ,{40} ,{50} ,{60} ,{70} ,{80} ,{90} ,{100} ,{110} ,{120} ,{130} ,{255} }; // Create a gray8_iamge_t instance, with height = 256, width = 256. gray8_image_t image(256,256); // Create a gray8_view_t instance of that image. gray8_view_t View = view(image); // You could do this by specifying a fill color in the ctor to image, // but that's no fun. int height = View.height(); int width = View.width(); for(int y=0; y<height; y++) { for(int x=0; x<width; x++) { View(x,y) = HistGram[x][y]; } } // Write png file with the image/view. //png_write_view("image.png",const_view(image)); png_write_view("image.png",View); // read image from the generated png file. gray8_image_t readImage(256, 256); // Read image from png file. png_read_image("image.png", readImage); // Create view for the image. gray8_view_t readView = view(readImage); // Now use 1D array to receive histogram, it's also ok to use a 2D array. int readHistogram[100]; int HisIndex = 0; // Assign the histogram with the value of view pixel. for (int x = 0; x < readView.height(); x++) { for (int y = 0; y < readView.width(); y++) { readHistogram[HisIndex] = readView(x,y); HisIndex++; } } return 0;}

 

 

Reference:

 

http://www.cppprog.com/boost_doc/libs/gil/doc/index.html

 

http://www.cppprog.com/2009/0305/76.html

 

http://pastebin.com/7V92Npm9