Fix softlight blend mode. Make nonseparable blends work with CMYK

Softlight blend mode was broken as the constants were not properly scaled
for 255 arithmetic.  The nonseparable blending code needs to do special
handling of K when the color space is CMYK.

1 files changed, 63 insertions, 24 deletions

diff --git a/source/fitz/draw-blend.c b/source/fitz/draw-blend.c
index 8694408d..17300ec7 100644
--- a/source/fitz/draw-blend.c
+++ b/source/fitz/draw-blend.c
@@ -100,14 +100,13 @@ static inline int fz_color_burn_byte(int b, int s)
 
 static inline int fz_soft_light_byte(int b, int s)
 {
-	/* review this */
 	if (s < 128) {
 		return b - fz_mul255(fz_mul255((255 - (s<<1)), b), 255 - b);
 	}
 	else {
 		int dbd;
 		if (b < 64)
-			dbd = fz_mul255(fz_mul255((b << 4) - 12, b) + 4, b);
+			dbd = fz_mul255(fz_mul255((b << 4) - 3060, b) + 1020, b);
 		else
 			dbd = (int)sqrtf(255.0f * b);
 		return b + fz_mul255(((s<<1) - 255), (dbd - b));
@@ -322,14 +321,14 @@ fz_blend_separable(byte * restrict bp, int bal, const byte * restrict sp, int sa
 }
 
 static void
-fz_blend_nonseparable(byte * restrict bp, int bal, const byte * restrict sp, int sal, int w, int blendmode)
+fz_blend_nonseparable(byte * restrict bp, int bal, const byte * restrict sp, int sal, int n, int w, int blendmode)
 {
 	do
 	{
 		unsigned char rr, rg, rb;
 
-		int sa = (sal ? sp[3] : 255);
-		int ba = (bal ? bp[3] : 255);
+		int sa = (sal ? sp[n] : 255);
+		int ba = (bal ? bp[n] : 255);
 		int saba = fz_mul255(sa, ba);
 
 		/* ugh, division to get non-premul components */
@@ -365,10 +364,29 @@ fz_blend_nonseparable(byte * restrict bp, int bal, const byte * restrict sp, int
 		bp[1] = fz_mul255(255 - sa, bp[1]) + fz_mul255(255 - ba, sp[1]) + fz_mul255(saba, rg);
 		bp[2] = fz_mul255(255 - sa, bp[2]) + fz_mul255(255 - ba, sp[2]) + fz_mul255(saba, rb);
 		if (bal)
-			bp[3] = ba + sa - saba;
+			bp[n] = ba + sa - saba;
 
-		sp += 3 + sal;
-		bp += 3 + bal;
+		/* Black */
+		if (n == 4)
+		{
+			int sk = (sp[3] * invsa) >> 8;
+			int bk = (bp[3] * invba) >> 8;
+
+			switch (blendmode)
+			{
+			default:
+			case FZ_BLEND_HUE:
+			case FZ_BLEND_SATURATION:
+			case FZ_BLEND_COLOR:
+				bp[3] = fz_mul255(bp[n], bk);
+				break;
+			case FZ_BLEND_LUMINOSITY:
+				bp[3] = fz_mul255(bp[n], sk);
+				break;
+			}
+		}
+		sp += n + sal;
+		bp += n + bal;
 	}
 	while (--w);
 }
@@ -507,7 +525,7 @@ fz_blend_separable_nonisolated(byte * restrict bp, int bal, const byte * restric
 }
 
 static inline void
-fz_blend_nonseparable_nonisolated(byte * restrict bp, int bal, const byte * restrict sp, int sal, int w, int blendmode, const byte * restrict hp, int alpha)
+fz_blend_nonseparable_nonisolated(byte * restrict bp, int bal, const byte * restrict sp, int sal, int n, int w, int blendmode, const byte * restrict hp, int alpha)
 {
 	do
 	{
@@ -515,14 +533,14 @@ fz_blend_nonseparable_nonisolated(byte * restrict bp, int bal, const byte * rest
 		int haa = fz_mul255(ha, alpha);
 		if (haa != 0)
 		{
-			int sa = (sal ? sp[3] : 255);
-			int ba = (bal ? bp[3] : 255);
+			int sa = (sal ? sp[n] : 255);
+			int ba = (bal ? bp[n] : 255);
 			int baha = fz_mul255(ba, haa);
 
 			/* Calculate result_alpha */
 			int ra = ba - baha + haa;
 			if (bal)
-				bp[3] = ra;
+				bp[n] = ra;
 			if (ra != 0)
 			{
 				/* Because we are a non-isolated group, we
@@ -578,11 +596,32 @@ fz_blend_nonseparable_nonisolated(byte * restrict bp, int bal, const byte * rest
 				bp[0] = fz_mul255(ra, rr);
 				bp[1] = fz_mul255(ra, rg);
 				bp[2] = fz_mul255(ra, rb);
+
+				/* Black */
+				if (n == 4)
+				{
+					int sk = (sp[3] * invsa) >> 8;
+					int bk = (bp[3] * invba) >> 8;
+					sk = (((sk - bk)*invha) >> 8) + bk;
+
+					switch (blendmode)
+					{
+					default:
+					case FZ_BLEND_HUE:
+					case FZ_BLEND_SATURATION:
+					case FZ_BLEND_COLOR:
+						bp[3] = fz_mul255(ra, bk);
+						break;
+					case FZ_BLEND_LUMINOSITY:
+						bp[3] = fz_mul255(ra, sk);
+						break;
+					}
+				}
 			}
 		}
 
-		sp += 3 + sal;
-		bp += 3 + bal;
+		sp += n + sal;
+		bp += n + bal;
 	}
 	while (--w);
 }
@@ -644,17 +683,17 @@ fz_blend_pixmap(fz_pixmap * restrict dst, fz_pixmap * restrict src, int alpha, i
 
 		while (h--)
 		{
-			if (n == 3 && blendmode >= FZ_BLEND_HUE)
+			if (blendmode >= FZ_BLEND_HUE)
 				if (da)
 					if (sa)
-						fz_blend_nonseparable_nonisolated(dp, 1, sp, 1, w, blendmode, hp, alpha);
+						fz_blend_nonseparable_nonisolated(dp, 1, sp, 1, n, w, blendmode, hp, alpha);
 					else
-						fz_blend_nonseparable_nonisolated(dp, 1, sp, 0, w, blendmode, hp, alpha);
+						fz_blend_nonseparable_nonisolated(dp, 1, sp, 0, n, w, blendmode, hp, alpha);
 				else
 					if (sa)
-						fz_blend_nonseparable_nonisolated(dp, 0, sp, 1, w, blendmode, hp, alpha);
+						fz_blend_nonseparable_nonisolated(dp, 0, sp, 1, n, w, blendmode, hp, alpha);
 					else
-						fz_blend_nonseparable_nonisolated(dp, 0, sp, 0, w, blendmode, hp, alpha);
+						fz_blend_nonseparable_nonisolated(dp, 0, sp, 0, n, w, blendmode, hp, alpha);
 			else
 				if (da)
 					if (sa)
@@ -675,17 +714,17 @@ fz_blend_pixmap(fz_pixmap * restrict dst, fz_pixmap * restrict src, int alpha, i
 	{
 		while (h--)
 		{
-			if (n == 3 && blendmode >= FZ_BLEND_HUE)
+			if (blendmode >= FZ_BLEND_HUE)
 				if (da)
 					if (sa)
-						fz_blend_nonseparable(dp, 1, sp, 1, w, blendmode);
+						fz_blend_nonseparable(dp, 1, sp, 1, n,  w, blendmode);
 					else
-						fz_blend_nonseparable(dp, 1, sp, 0, w, blendmode);
+						fz_blend_nonseparable(dp, 1, sp, 0, n,  w, blendmode);
 				else
 					if (sa)
-						fz_blend_nonseparable(dp, 0, sp, 1, w, blendmode);
+						fz_blend_nonseparable(dp, 0, sp, 1, n, w, blendmode);
 					else
-						fz_blend_nonseparable(dp, 0, sp, 0, w, blendmode);
+						fz_blend_nonseparable(dp, 0, sp, 0, n,  w, blendmode);
 			else
 				if (da)
 					if (sa)