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-rw-r--r--src/core/SkDither.h198
1 files changed, 198 insertions, 0 deletions
diff --git a/src/core/SkDither.h b/src/core/SkDither.h
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+++ b/src/core/SkDither.h
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+
+/*
+ * Copyright 2008 The Android Open Source Project
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+
+#ifndef SkDither_DEFINED
+#define SkDither_DEFINED
+
+#include "SkColorPriv.h"
+
+#define SK_DitherValueMax4444 15
+#define SK_DitherValueMax565 7
+
+/* need to use macros for bit-counts for each component, and then
+ move these into SkColorPriv.h
+*/
+
+#define SkDITHER_R32_FOR_565_MACRO(r, d) (r + d - (r >> 5))
+#define SkDITHER_G32_FOR_565_MACRO(g, d) (g + (d >> 1) - (g >> 6))
+#define SkDITHER_B32_FOR_565_MACRO(b, d) (b + d - (b >> 5))
+
+#define SkDITHER_A32_FOR_4444_MACRO(a, d) (a + 15 - (a >> 4))
+#define SkDITHER_R32_FOR_4444_MACRO(r, d) (r + d - (r >> 4))
+#define SkDITHER_G32_FOR_4444_MACRO(g, d) (g + d - (g >> 4))
+#define SkDITHER_B32_FOR_4444_MACRO(b, d) (b + d - (b >> 4))
+
+#ifdef SK_DEBUG
+ inline unsigned SkDITHER_R32_FOR_565(unsigned r, unsigned d)
+ {
+ SkASSERT(d <= SK_DitherValueMax565);
+ SkA32Assert(r);
+ r = SkDITHER_R32_FOR_565_MACRO(r, d);
+ SkA32Assert(r);
+ return r;
+ }
+ inline unsigned SkDITHER_G32_FOR_565(unsigned g, unsigned d)
+ {
+ SkASSERT(d <= SK_DitherValueMax565);
+ SkG32Assert(g);
+ g = SkDITHER_G32_FOR_565_MACRO(g, d);
+ SkG32Assert(g);
+ return g;
+ }
+ inline unsigned SkDITHER_B32_FOR_565(unsigned b, unsigned d)
+ {
+ SkASSERT(d <= SK_DitherValueMax565);
+ SkB32Assert(b);
+ b = SkDITHER_B32_FOR_565_MACRO(b, d);
+ SkB32Assert(b);
+ return b;
+ }
+#else
+ #define SkDITHER_R32_FOR_565(r, d) SkDITHER_R32_FOR_565_MACRO(r, d)
+ #define SkDITHER_G32_FOR_565(g, d) SkDITHER_G32_FOR_565_MACRO(g, d)
+ #define SkDITHER_B32_FOR_565(b, d) SkDITHER_B32_FOR_565_MACRO(b, d)
+#endif
+
+#define SkDITHER_R32To565(r, d) SkR32ToR16(SkDITHER_R32_FOR_565(r, d))
+#define SkDITHER_G32To565(g, d) SkG32ToG16(SkDITHER_G32_FOR_565(g, d))
+#define SkDITHER_B32To565(b, d) SkB32ToB16(SkDITHER_B32_FOR_565(b, d))
+
+#define SkDITHER_A32To4444(a, d) SkA32To4444(SkDITHER_A32_FOR_4444_MACRO(a, d))
+#define SkDITHER_R32To4444(r, d) SkR32To4444(SkDITHER_R32_FOR_4444_MACRO(r, d))
+#define SkDITHER_G32To4444(g, d) SkG32To4444(SkDITHER_G32_FOR_4444_MACRO(g, d))
+#define SkDITHER_B32To4444(b, d) SkB32To4444(SkDITHER_B32_FOR_4444_MACRO(b, d))
+
+static inline SkPMColor SkDitherARGB32For565(SkPMColor c, unsigned dither)
+{
+ SkASSERT(dither <= SK_DitherValueMax565);
+
+ unsigned sa = SkGetPackedA32(c);
+ dither = SkAlphaMul(dither, SkAlpha255To256(sa));
+
+ unsigned sr = SkGetPackedR32(c);
+ unsigned sg = SkGetPackedG32(c);
+ unsigned sb = SkGetPackedB32(c);
+ sr = SkDITHER_R32_FOR_565(sr, dither);
+ sg = SkDITHER_G32_FOR_565(sg, dither);
+ sb = SkDITHER_B32_FOR_565(sb, dither);
+
+ return SkPackARGB32(sa, sr, sg, sb);
+}
+
+static inline SkPMColor SkDitherRGB32For565(SkPMColor c, unsigned dither)
+{
+ SkASSERT(dither <= SK_DitherValueMax565);
+
+ unsigned sr = SkGetPackedR32(c);
+ unsigned sg = SkGetPackedG32(c);
+ unsigned sb = SkGetPackedB32(c);
+ sr = SkDITHER_R32_FOR_565(sr, dither);
+ sg = SkDITHER_G32_FOR_565(sg, dither);
+ sb = SkDITHER_B32_FOR_565(sb, dither);
+
+ return SkPackARGB32(0xFF, sr, sg, sb);
+}
+
+static inline uint16_t SkDitherRGBTo565(U8CPU r, U8CPU g, U8CPU b,
+ unsigned dither)
+{
+ SkASSERT(dither <= SK_DitherValueMax565);
+ r = SkDITHER_R32To565(r, dither);
+ g = SkDITHER_G32To565(g, dither);
+ b = SkDITHER_B32To565(b, dither);
+ return SkPackRGB16(r, g, b);
+}
+
+static inline uint16_t SkDitherRGB32To565(SkPMColor c, unsigned dither)
+{
+ SkASSERT(dither <= SK_DitherValueMax565);
+
+ unsigned sr = SkGetPackedR32(c);
+ unsigned sg = SkGetPackedG32(c);
+ unsigned sb = SkGetPackedB32(c);
+ sr = SkDITHER_R32To565(sr, dither);
+ sg = SkDITHER_G32To565(sg, dither);
+ sb = SkDITHER_B32To565(sb, dither);
+
+ return SkPackRGB16(sr, sg, sb);
+}
+
+static inline uint16_t SkDitherARGB32To565(U8CPU sa, SkPMColor c, unsigned dither)
+{
+ SkASSERT(dither <= SK_DitherValueMax565);
+ dither = SkAlphaMul(dither, SkAlpha255To256(sa));
+
+ unsigned sr = SkGetPackedR32(c);
+ unsigned sg = SkGetPackedG32(c);
+ unsigned sb = SkGetPackedB32(c);
+ sr = SkDITHER_R32To565(sr, dither);
+ sg = SkDITHER_G32To565(sg, dither);
+ sb = SkDITHER_B32To565(sb, dither);
+
+ return SkPackRGB16(sr, sg, sb);
+}
+
+///////////////////////// 4444
+
+static inline SkPMColor16 SkDitherARGB32To4444(U8CPU a, U8CPU r, U8CPU g,
+ U8CPU b, unsigned dither)
+{
+ dither = SkAlphaMul(dither, SkAlpha255To256(a));
+
+ a = SkDITHER_A32To4444(a, dither);
+ r = SkDITHER_R32To4444(r, dither);
+ g = SkDITHER_G32To4444(g, dither);
+ b = SkDITHER_B32To4444(b, dither);
+
+ return SkPackARGB4444(a, r, g, b);
+}
+
+static inline SkPMColor16 SkDitherARGB32To4444(SkPMColor c, unsigned dither)
+{
+ unsigned a = SkGetPackedA32(c);
+ unsigned r = SkGetPackedR32(c);
+ unsigned g = SkGetPackedG32(c);
+ unsigned b = SkGetPackedB32(c);
+
+ dither = SkAlphaMul(dither, SkAlpha255To256(a));
+
+ a = SkDITHER_A32To4444(a, dither);
+ r = SkDITHER_R32To4444(r, dither);
+ g = SkDITHER_G32To4444(g, dither);
+ b = SkDITHER_B32To4444(b, dither);
+
+ return SkPackARGB4444(a, r, g, b);
+}
+
+// TODO: need dither routines for 565 -> 4444
+
+// this toggles between a 4x4 and a 1x4 array
+//#define ENABLE_DITHER_MATRIX_4X4
+
+#ifdef ENABLE_DITHER_MATRIX_4X4
+ extern const uint8_t gDitherMatrix_4Bit_4X4[4][4];
+ extern const uint8_t gDitherMatrix_3Bit_4X4[4][4];
+
+ #define DITHER_4444_SCAN(y) const uint8_t* dither_scan = gDitherMatrix_4Bit_4X4[(y) & 3]
+ #define DITHER_565_SCAN(y) const uint8_t* dither_scan = gDitherMatrix_3Bit_4X4[(y) & 3]
+
+ #define DITHER_VALUE(x) dither_scan[(x) & 3]
+#else
+ extern const uint16_t gDitherMatrix_4Bit_16[4];
+ extern const uint16_t gDitherMatrix_3Bit_16[4];
+
+ #define DITHER_4444_SCAN(y) const uint16_t dither_scan = gDitherMatrix_4Bit_16[(y) & 3]
+ #define DITHER_565_SCAN(y) const uint16_t dither_scan = gDitherMatrix_3Bit_16[(y) & 3]
+
+ #define DITHER_VALUE(x) ((dither_scan >> (((x) & 3) << 2)) & 0xF)
+#endif
+
+#define DITHER_INC_X(x) ++(x)
+
+#endif
generated by cgit v1.2.3 (git 2.39.1) at 2024-08-18 09:24:14 +0000