CPU impl for ToSRGBColorFilter

Change-Id: Idf445e661997a86517cd4d07e50f3cbe5d219a7e
Reviewed-on: https://skia-review.googlesource.com/26520
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

1 files changed, 40 insertions, 26 deletions

diff --git a/src/core/SkPM4fPriv.h b/src/core/SkPM4fPriv.h
index 2789d3763e..0ded5e5116 100644
--- a/src/core/SkPM4fPriv.h
+++ b/src/core/SkPM4fPriv.h
@@ -99,51 +99,65 @@ static inline void analyze_3x4_matrix(const float matrix[12],
     *can_overflow  =  overflow;
 }
 
-
 // N.B. scratch_matrix_3x4 must live at least as long as p.
-static inline void append_gamut_transform(SkRasterPipeline* p, float scratch_matrix_3x4[12],
-                                          SkColorSpace* src, SkColorSpace* dst,
-                                          SkAlphaType alphaType) {
-    if (src == dst) { return; }   // That was easy.
-    if (!dst)       { return; }   // Legacy modes intentionally ignore color gamut.
-    if (!src)       { return; }   // A null src color space means linear gamma, dst gamut.
-
-    auto toXYZ = as_CSB(src)->  toXYZD50(),
-       fromXYZ = as_CSB(dst)->fromXYZD50();
-    if (!toXYZ || !fromXYZ) {
-        SkASSERT(false);  // We really don't want to get here with a weird colorspace.
-        return;
+// Returns false if no gamut tranformation was necessary.
+static inline bool append_gamut_transform_noclamp(SkRasterPipeline* p,
+                                                  float scratch_matrix_3x4[12],
+                                                  SkColorSpace* src,
+                                                  SkColorSpace* dst) {
+    if (src == dst || !dst || !src) {
+        return false;
+    }
+
+    const SkMatrix44 *fromSrc = as_CSB(src)->  toXYZD50(),
+                       *toDst = as_CSB(dst)->fromXYZD50();
+    if (!fromSrc || !toDst) {
+        SkDEBUGFAIL("We can't handle non-XYZ color spaces in append_gamut_transform().");
+        return false;
     }
 
     // Slightly more sophisticated version of if (src == dst)
     if (as_CSB(src)->toXYZD50Hash() == as_CSB(dst)->toXYZD50Hash()) {
-        return;
+        return false;
     }
 
-    SkMatrix44 m44(*fromXYZ, *toXYZ);
-
     // Convert from 4x4 to (column-major) 3x4.
+    SkMatrix44 m44(*toDst, *fromSrc);
     auto ptr = scratch_matrix_3x4;
     *ptr++ = m44.get(0,0); *ptr++ = m44.get(1,0); *ptr++ = m44.get(2,0);
     *ptr++ = m44.get(0,1); *ptr++ = m44.get(1,1); *ptr++ = m44.get(2,1);
     *ptr++ = m44.get(0,2); *ptr++ = m44.get(1,2); *ptr++ = m44.get(2,2);
     *ptr++ = m44.get(0,3); *ptr++ = m44.get(1,3); *ptr++ = m44.get(2,3);
 
-    bool needs_clamp_0, needs_clamp_1;
-    analyze_3x4_matrix(scratch_matrix_3x4, &needs_clamp_0, &needs_clamp_1);
-
     p->append(SkRasterPipeline::matrix_3x4, scratch_matrix_3x4);
-    if (needs_clamp_0) { p->append(SkRasterPipeline::clamp_0); }
-    if (needs_clamp_1) {
-        (kPremul_SkAlphaType == alphaType) ? p->append(SkRasterPipeline::clamp_a)
-                                           : p->append(SkRasterPipeline::clamp_1);
+    return true;
+}
+
+
+// N.B. scratch_matrix_3x4 must live at least as long as p.
+static inline void append_gamut_transform(SkRasterPipeline* p,
+                                          float scratch_matrix_3x4[12],
+                                          SkColorSpace* src,
+                                          SkColorSpace* dst,
+                                          SkAlphaType alphaType) {
+    if (append_gamut_transform_noclamp(p, scratch_matrix_3x4, src, dst)) {
+        bool needs_clamp_0, needs_clamp_1;
+        analyze_3x4_matrix(scratch_matrix_3x4, &needs_clamp_0, &needs_clamp_1);
+
+        if (needs_clamp_0) { p->append(SkRasterPipeline::clamp_0); }
+        if (needs_clamp_1) {
+            (kPremul_SkAlphaType == alphaType) ? p->append(SkRasterPipeline::clamp_a)
+                                               : p->append(SkRasterPipeline::clamp_1);
+        }
     }
 }
 
-static inline void append_gamut_transform(SkRasterPipeline* p, SkArenaAlloc* scratch,
-                                          SkColorSpace* src, SkColorSpace* dst,
+static inline void append_gamut_transform(SkRasterPipeline* p,
+                                          SkArenaAlloc* alloc,
+                                          SkColorSpace* src,
+                                          SkColorSpace* dst,
                                           SkAlphaType alphaType) {
-    append_gamut_transform(p, scratch->makeArrayDefault<float>(12), src, dst, alphaType);
+    append_gamut_transform(p, alloc->makeArrayDefault<float>(12), src, dst, alphaType);
 }
 
 static inline SkColor4f to_colorspace(const SkColor4f& c, SkColorSpace* src, SkColorSpace* dst) {