png_set_rgb_to_gray  676 third_party/libpng/pngrtran.c png_set_rgb_to_gray(png_structp png_ptr, int error_action, double red,
png_set_rgb_to_gray  411 third_party/libpng/pngusr.h #define png_set_rgb_to_gray             wk_png_set_rgb_to_gray