/* make an image of size x by y whose pixels are their coordinates.
 */
make_xy x y = im_make_xy (to_real x) (to_real y);

/* make an image with the specified properties ... pixel is (eg.) 
 * Vector [0, 0, 0], or 12. If coding == labq, we ignore bands, format and
 * type, generate a 3 band float image, and lab2labq it before handing it
 * back.
 */
image_new w h b fmt coding type pixel xoff yoff
	= im''''
{
	b'
		= 3, coding == Image_coding.LABPACK
		= b;
	fmt'
		= Image_format.FLOAT, coding == Image_coding.LABPACK
		= fmt;
	type'
		= Image_type.LAB, coding == Image_coding.LABPACK
		= type;

	im = im_black (to_real w) (to_real h) (to_real b') + pixel;

	im' = clip2fmt fmt' im;

	im'' 
		= im_Lab2LabQ im', coding == Image_coding.LABPACK;
		= im';

	im''' = image_set_type type' im'';
	im'''' = image_set_origin xoff yoff im''';
}

/* generate a slice of LAB space size x size pixels for L* == l
 */
lab_slice size l 
	= image_set_type Image_type.LAB im
{
    L = image_new size size 1
		Image_format.FLOAT Image_coding.NOCODING Image_type.B_W l 0 0;
	A1 = im_fgrey (to_real size) (to_real size);

	/* im_fgrey always makes 0-1, so these ranges can be wired in.
	 */
	A2 = A1 * 256 - 128;

	A4 = im_rot90 A2;
	im = image_set_origin (size / 2) (size / 2) (L ++ A2 ++ A4);
}

/* Look at Image, try to make a Colour (failing that, a Vector) which is white
 * for that image type.
 */
image_white im
	= colour_transform_to type white_lab,
		bands == 3 && coding == Image_coding.NOCODING &&
		colour_spaces.present 1 type
	= white_lab,
		coding == Image_coding.LABPACK
	= Vector (replicate bands (max_value.lookup 1 0 format))
{
	bands = im.bands;
	type = im.type;
	format = im.format;
	coding = im.coding;
	colour_spaces = Image_type.colour_spaces;

	// white as LAB
	white_lab = Colour "Lab" [100, 0, 0];

	// maximum value for this numeric type
	max_value = Table [
		[255, Image_format.DPCOMPLEX],
		[255, Image_format.DOUBLE],
		[255, Image_format.COMPLEX],
		[255, Image_format.FLOAT],
		[2 ** 31 - 1, Image_format.INT],
		[2 ** 32 - 1, Image_format.UINT],
		[2 ** 15 - 1, Image_format.SHORT],
		[2 ** 16 - 1, Image_format.USHORT],
		[2 ** 7 - 1, Image_format.CHAR],
		[2 ** 8 - 1, Image_format.UCHAR]
	];
}

/* Make a seperable gaussian mask.
 */
matrix_gaussian_blur radius
        = Matrix_con mask_g_sum 0 [mask_g_line]
{
        mask_g = im_gauss_imask (radius / 3) 0.2;
        mask_g_line = mask_g.value?(mask_g.height / 2);
        mask_g_sum = foldr1 add mask_g_line;
}

/* Make a seperable square mask.
 */
matrix_blur radius
        = Matrix_con (foldr1 add mask_sq_line) 0 [mask_sq_line]
{
        mask_sq_line = replicate (2 * radius - 1) 1; 
}