_php_image_bw_convert  139 gd.c           static void _php_image_bw_convert(gdImagePtr im_org, gdIOCtx *out, int threshold);
_php_image_bw_convert 4356 gd.c           	_php_image_output(INTERNAL_FUNCTION_PARAM_PASSTHRU, PHP_GDIMG_CONVERT_WBM, "WBMP", _php_image_bw_convert);