separate out rgb2{linear,gamma}

PDLPorters · Jan 11, 2023 · 73e4f76 · 73e4f76
1 parent f524e5c
commit 73e4f76
Show file tree

Hide file tree

Showing 3 changed files with 37 additions and 22 deletions.
diff --git a/color_space.c b/color_space.c
@@ -189,37 +189,50 @@ void hsv2rgb( double *hsv, double *rgb )
 
 void rgb2xyz( double *rgb, double gamma, double *m0, double *m1, double *m2, double *xyz )
 {
-	double copy[] = { rgb[0], rgb[1], rgb[2] };
-	/* weighted RGB */
+	rgb2linear(rgb, gamma, xyz);
+	struct pixel  p = { xyz[0], xyz[1], xyz[2] };
+	_mult_v3_m33( &p, m0, m1, m2, xyz );
+}
+
+
+void rgb2linear( double *rgb, double gamma, double *out )
+{
 	int i;
-	if (gamma < 0) {
-		/* special case for sRGB gamma curve */
-		for (i = 0; i < 3; i++)
-		  if ( fabs(copy[i]) <= 0.04045 ) { copy[i] /= 12.92; }
-		  else { copy[i] = _apow( (copy[i] + 0.055)/1.055, 2.4 ); }
-	}
-	else {
-		for (i = 0; i < 3; i++)
-		  copy[i] = _apow(copy[i], gamma);
+	if (gamma < 0) { /* special case for sRGB gamma curve */
+	  for (i = 0; i < 3; i++)
+	    out[i] = fabs(rgb[i]) <= 0.04045 ? rgb[i] / 12.92 : _apow( (rgb[i] + 0.055)/1.055, 2.4 );
+	} else if (gamma == 1.0) { /* copy if different locations */
+	  if (rgb != out)
+	    for (i = 0; i < 3; i++)
+	      out[i] = rgb[i];
+	} else {
+	  for (i = 0; i < 3; i++)
+	    out[i] = _apow(rgb[i], gamma);
 	}
-	struct pixel  p = { copy[0], copy[1], copy[2] };
-	_mult_v3_m33( &p, m0, m1, m2, xyz );
 }
 
 
 void xyz2rgb( double *xyz, double gamma, double *m0, double *m1, double *m2, double *rgb )
 {
 	struct pixel  p = { xyz[0], xyz[1], xyz[2] };
 	_mult_v3_m33( &p, m0, m1, m2, rgb );
+	rgb2gamma(rgb, gamma, rgb);
+}
+
+
+void rgb2gamma( double *rgb, double gamma, double *out )
+{
 	int i;
-	if (gamma < 0) {
-		/* special case for sRGB gamma curve */
-		for (i = 0; i < 3; i++)
-		  rgb[i] = (fabs(rgb[i]) <= 0.0031308) ? 12.92 * rgb[i]  :  1.055 * _apow(rgb[i], 1.0/2.4) - 0.055;
-	}
-	else {
-		for (i = 0; i < 3; i++)
-		  rgb[i] = _apow(rgb[i], 1.0 / gamma);
+	if (gamma < 0) { /* special case for sRGB gamma curve */
+	  for (i = 0; i < 3; i++)
+	    out[i] = (fabs(rgb[i]) <= 0.0031308) ? 12.92 * rgb[i] : 1.055 * _apow(rgb[i], 1.0/2.4) - 0.055;
+	} else if (gamma == 1.0) { /* copy if different locations */
+	  if (rgb != out)
+	    for (i = 0; i < 3; i++)
+	      out[i] = rgb[i];
+	} else {
+	  for (i = 0; i < 3; i++)
+	    out[i] = _apow(rgb[i], 1.0 / gamma);
 	}
 }
 

diff --git a/color_space.h b/color_space.h
@@ -8,6 +8,8 @@ void    rgb2hsv( double *rgb, double *hsv );
 void    hsv2rgb( double *hsv, double *rgb );
 void    rgb2xyz( double *rgb, double gamma, double *m0, double *m1, double *m2, double *xyz );
 void    xyz2rgb( double *xyz, double gamma, double *m0, double *m1, double *m2, double *rgb );
+void    rgb2linear( double *rgb, double gamma, double *out );
+void    rgb2gamma( double *rgb, double gamma, double *out );
 void    xyY2xyz( double *xyY, double *xyz );
 void    xyz2lab( double *xyz, double *w, double *lab );
 void    lab2lch( double *lab, double *lch );

diff --git a/t/color_space.t b/t/color_space.t
@@ -98,7 +98,7 @@ sub tapprox {
 	my $rgb_ = pdl(255, 10, 50) / 255;
 	my $a = rgb_to_xyz( $rgb_, 'Adobe' );
 	my $ans = pdl( 0.582073320819542, 0.299955362786115, 0.0546021884576833 ); 
-	ok( tapprox( $a, $ans), 'rgb_to_xyz Adobe' ) or diag($a, $ans);
+	ok( tapprox( $a, $ans), 'rgb_to_xyz Adobe' ) or diag($a, "\n", $ans);
 }
 
 # xyY_to_xyz