setalpha_rgba_rgba
Tcl_Obj* imageObj
Tcl_Obj* imageAlphaObj

/*
 * Replace the input's alpha channel with the alpha channel of the second
 * image. IOW, copy the second image's alpha channel over into the first.
 */

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

crimp_input (imageObj,      image,  rgba);
crimp_input (imageAlphaObj, imageA, rgba);

if (!crimp_eq_dim (image, imageA)) {
    Tcl_SetResult(interp, "image dimensions do not match", TCL_STATIC);
    return TCL_ERROR;
}

result = crimp_new_like (image);

for (y = 0; y < result->h; y++) {
    for (x = 0; x < result->w; x++) {
	R (result, x, y) = R (image, x, y);
	G (result, x, y) = G (image, x, y);
	B (result, x, y) = B (image, x, y);
	A (result, x, y) = A (imageA, x, y);
    }
}

Tcl_SetObjResult(interp, crimp_new_image_obj (result));
return TCL_OK;

/* vim: set sts=4 sw=4 tw=80 et ft=c: */
/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */