*
*
* References:
+ * - A Review of RGB Color Spaces, Danny Pascale (2003)
+ * - http://www.adobe.com/digitalimag/pdfs/AdobeRGB1998.pdf
* - http://www.tecgraf.puc-rio.br/~mgattass/color/ColorIndex.html
*
* FIXME:
* - SIMD should help to speed up conversion of large arrays
* - maybe try to generate a long switch in color_conv_pixel()
* with optimized entries instead of access to interpolation table
+ * - most of multiplications in srgb_to_luv_pixels can be replaced
+ * with tables lookup... tests shows almost the same speed for random
+ * input and cca 40% gain when input colors fit in CPU chache
*/
#ifndef _IMAGES_COLOR_H
#define _IMAGES_COLOR_H
+#include "images/images.h"
+
+// A comparison of four multimedia RGB spaces, Danny Pascale
+
+enum {
+ COLOR_SPACE_UNKNOWN = 0,
+ COLOR_SPACE_GRAYSCALE,
+ COLOR_SPACE_RGB,
+ COLOR_SPACE_XYZ,
+ COLOR_SPACE_LAB,
+ COLOR_SPACE_LUV,
+ COLOR_SPACE_YCBCR,
+ COLOR_SPACE_MAX
+};
+
+/* Color spaces in the CIE 1931 chromacity diagram */
+
+struct color_space_chromacity_info {
+ double prim1[2];
+ double prim2[2];
+ double prim3[2];
+ double white[2];
+};
+
+struct color_space_gamma_info {
+ double simple_gamma;
+ double detailed_gamma;
+ double offset;
+ double transition;
+ double slope;
+};
+
+struct color_space_info {
+ byte *name;
+ struct color_space_chromacity_info chromacity;
+ struct color_space_gamma_info gamma;
+};
+
+extern const double
+ color_illuminant_d50[2],
+ color_illuminant_d65[2],
+ color_illuminant_e[2];
+
+extern const struct color_space_info
+ color_adobe_rgb_info, /* Adobe RGB (1998) */
+ color_apple_rgb_info, /* Apple RGB */
+ color_cie_rgb_info, /* CIE RGB */
+ color_color_match_rgb_info, /* ColorMatch RGB */
+ color_srgb_info; /* sRGB */
+
+/* These routines do not check numeric errors! */
+void color_compute_color_space_to_xyz_matrix(double matrix[9], const struct color_space_chromacity_info *space);
+void color_compute_bradford_matrix(double matrix[9], const double src[2], const double dest[2]);
+void color_compute_color_spaces_conversion_matrix(double matrix[9], const struct color_space_chromacity_info *src, const struct color_space_chromacity_info *dest);
+void color_invert_matrix(double dest[9], double matrix[9]);
+
+static inline uns
+rgb_to_gray_func(uns r, uns g, uns b)
+{
+ return (r * 19660 + g * 38666 + b * 7210) >> 16;
+}
+
+extern struct color color_black, color_white;
+
+static inline void
+color_make_gray(struct color *color, uns gray)
+{
+ color->c[0] = gray;
+ color->color_space = COLOR_SPACE_GRAYSCALE;
+}
+
+static inline void
+color_make_rgb(struct color *color, uns r, uns g, uns b)
+{
+ color->c[0] = r;
+ color->c[1] = g;
+ color->c[2] = b;
+ color->color_space = COLOR_SPACE_RGB;
+}
+
+void color_put_color_space(byte *dest, struct color *color, uns color_space);
+void color_put_grayscale(byte *dest, struct color *color);
+void color_put_rgb(byte *dest, struct color *color);
+
/* Exact slow conversion routines */
-void srgb_to_xyz_slow(double dest[3], double src[3]);
-void xyz_to_luv_slow(double dest[3], double src[3]);
+void srgb_to_xyz_exact(double dest[3], double src[3]);
+void xyz_to_srgb_exact(double dest[3], double src[3]);
+void xyz_to_luv_exact(double dest[3], double src[3]);
+void luv_to_xyz_exact(double dest[3], double src[3]);
/* Reference white */
#define REF_WHITE_X 0.96422
void srgb_to_luv_init(void);
void srgb_to_luv_pixels(byte *dest, byte *src, uns count);
+/* L covers the interval [0..255]; u and v are centered to 128 and scaled by 1/4 in respect of L */
static inline void
srgb_to_luv_pixel(byte *dest, byte *src)
{