235     NSInteger size = width * height * 4;

   235     NSInteger size = width * height * 4;

   236     GLubyte *buffer = (GLubyte *) malloc(size * sizeof(GLubyte));

   236     GLubyte *buffer = (GLubyte *) malloc(size * sizeof(GLubyte));

   237     GLubyte *buffer_flipped = (GLubyte *) malloc(size * sizeof(GLubyte));

   237     GLubyte *buffer_flipped = (GLubyte *) malloc(size * sizeof(GLubyte));

   238 

   238 

   239     glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);

   239     glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);

   241     // flip the data as glReadPixels here reads upside down

   241     // flip the data as glReadPixels here reads upside down

   242     for(int y = 0; y <height; y++)

   242     for(int y = 0; y <height; y++)

   243         for(int x = 0; x <width * 4; x++)

   243         for(int x = 0; x <width * 4; x++)

   244             buffer_flipped[(int)((height - 1 - y) * width * 4 + x)] = buffer[(int)(y * 4 * width + x)];

   244             buffer_flipped[(int)((height - 1 - y) * width * 4 + x)] = buffer[(int)(y * 4 * width + x)];

   245     free(buffer);

   245     free(buffer);