png_set_background

Name

png_set_background -- set the background for given image

Synopsis

#include <png.h>

void png_set_background(png_structp png_ptr, png_color_16p background_color, int background_gamma_code, int need_expand, double background_gamma);

Description

png_set_background() shall set the background of an image with alpha channel or simple transparency with the specified background color. If background_gamma_code is set to PNG_BACKGROUND_GAMMA_SCREEN, it indicates that the supplied background color is in the gamma space of the display, else if it is set to PNG_BACKGROUND_GAMMA_FILE, the color is in the gamma space of the file. If the background color is supplied at the original bit-depth for a grayscale image that is expanded to truecolor or to a higher bit-depth, need_expand must be set to 1, but if the background color is supplied at the expanded bit-depth, need_expand must be set to 0. Similarly for paletted images, if background color is supplied as a palette index, need_expand must be set to 1, else if background color is supplied as an RGB triplet, need_expand must be set to 0.