convert_2grey8_rgba
Tcl_Obj* imageObj

crimp_image* image;
crimp_image* result;
int          x, y;

crimp_input (imageObj, image, rgba);

result = crimp_new_grey8 (image->w, image->h);

for (y = 0; y < image->h; y++) {
    for (x = 0; x < image->w; x++) {

	/*
	 * This conversion to a grey scale is based on the ITU-R 601-2 luma
	 * transform computing the "luminosity" of each pixel.
	 *
	 * Note: The factors for R, G, and B add up to 1000, which means that
	 * after the scaling division the result is in the range 0..255
	 * without requiring clamping.
	 */

	GREY8 (result, x, y) = 
	  (299 * R (image, x, y) +
	   587 * G (image, x, y) +
	   114 * B (image, x, y))/1000;

    }
}

Tcl_SetObjResult(interp, crimp_new_image_obj (result));
return TCL_OK;


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