Function writeTextureToFile

examples/OpenGLWindow/SimpleOpenGL3App.cpp:1016–1074

//#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "stb_image/stb_image_write.h"
static void writeTextureToFile(int textureWidth, int textureHeight, const char* fileName, FILE* ffmpegVideo)
{
	int numComponents = 4;
	//glPixelStorei(GL_PACK_ALIGNMENT,1);

	b3Assert(glGetError() == GL_NO_ERROR);
	//glReadBuffer(GL_BACK);//COLOR_ATTACHMENT0);

	float* orgPixels = (float*)malloc(textureWidth * textureHeight * numComponents * 4);
	glReadPixels(0, 0, textureWidth, textureHeight, GL_RGBA, GL_FLOAT, orgPixels);
	//it is useful to have the actual float values for debugging purposes

	//convert float->char
	char* pixels = (char*)malloc(textureWidth * textureHeight * numComponents);
	assert(glGetError() == GL_NO_ERROR);

	for (int j = 0; j < textureHeight; j++)
	{
		for (int i = 0; i < textureWidth; i++)
		{
			pixels[(j * textureWidth + i) * numComponents] = char(orgPixels[(j * textureWidth + i) * numComponents] * 255.f);
			pixels[(j * textureWidth + i) * numComponents + 1] = char(orgPixels[(j * textureWidth + i) * numComponents + 1] * 255.f);
			pixels[(j * textureWidth + i) * numComponents + 2] = char(orgPixels[(j * textureWidth + i) * numComponents + 2] * 255.f);
			pixels[(j * textureWidth + i) * numComponents + 3] = char(orgPixels[(j * textureWidth + i) * numComponents + 3] * 255.f);
		}
	}

	if (ffmpegVideo)
	{
		fwrite(pixels, textureWidth * textureHeight * numComponents, 1, ffmpegVideo);
		//fwrite(pixels, 100,1,ffmpegVideo);//textureWidth*textureHeight*numComponents, 1, ffmpegVideo);
	}
	else
	{
		if (1)
		{
			//swap the pixels
			unsigned char tmp;

			for (int j = 0; j < textureHeight / 2; j++)
			{
				for (int i = 0; i < textureWidth; i++)
				{
					for (int c = 0; c < numComponents; c++)
					{
						tmp = pixels[(j * textureWidth + i) * numComponents + c];
						pixels[(j * textureWidth + i) * numComponents + c] =
							pixels[((textureHeight - j - 1) * textureWidth + i) * numComponents + c];
						pixels[((textureHeight - j - 1) * textureWidth + i) * numComponents + c] = tmp;
					}
				}
			}
		}
		stbi_write_png(fileName, textureWidth, textureHeight, numComponents, pixels, textureWidth * numComponents);
	}

	free(pixels);
	free(orgPixels);