add SkLerpXfermode
BUG=
R=bsalomon@google.com
Review URL: https://codereview.chromium.org/15602003
git-svn-id: http://skia.googlecode.com/svn/trunk@9229 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/effects/SkLerpXfermode.cpp b/src/effects/SkLerpXfermode.cpp
new file mode 100644
index 0000000..d73ecf4
--- /dev/null
+++ b/src/effects/SkLerpXfermode.cpp
@@ -0,0 +1,110 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkLerpXfermode.h"
+#include "SkColorPriv.h"
+#include "SkFlattenableBuffers.h"
+#include "SkString.h"
+
+SkXfermode* SkLerpXfermode::Create(SkScalar scale) {
+ int scale256 = SkScalarRoundToInt(scale * 256);
+ if (scale256 >= 256) {
+ return SkXfermode::Create(SkXfermode::kSrc_Mode);
+ } else if (scale256 <= 0) {
+ return SkXfermode::Create(SkXfermode::kDst_Mode);
+ }
+ return SkNEW_ARGS(SkLerpXfermode, (scale256));
+}
+
+SkLerpXfermode::SkLerpXfermode(unsigned scale256) : fScale256(scale256) {}
+
+SkLerpXfermode::SkLerpXfermode(SkFlattenableReadBuffer& buffer)
+ : INHERITED(buffer) {
+ fScale256 = buffer.readUInt();
+}
+
+void SkLerpXfermode::flatten(SkFlattenableWriteBuffer& buffer) const {
+ this->INHERITED::flatten(buffer);
+ buffer.writeUInt(fScale256);
+}
+
+void SkLerpXfermode::xfer32(SkPMColor dst[], const SkPMColor src[], int count,
+ const SkAlpha aa[]) const {
+ const int scale = fScale256;
+
+ if (aa) {
+ for (int i = 0; i < count; ++i) {
+ unsigned a = aa[i];
+ if (a) {
+ SkPMColor dstC = dst[i];
+ SkPMColor resC = SkFastFourByteInterp256(src[i], dstC, scale);
+ if (a < 255) {
+ resC = SkFastFourByteInterp256(resC, dstC, a + (a >> 7));
+ }
+ dst[i] = resC;
+ }
+ }
+ } else {
+ for (int i = 0; i < count; ++i) {
+ dst[i] = SkFastFourByteInterp256(src[i], dst[i], scale);
+ }
+ }
+}
+
+void SkLerpXfermode::xfer16(uint16_t dst[], const SkPMColor src[], int count,
+ const SkAlpha aa[]) const {
+ const int scale = fScale256;
+
+ if (aa) {
+ for (int i = 0; i < count; ++i) {
+ unsigned a = aa[i];
+ if (a) {
+ SkPMColor dstC = SkPixel16ToPixel32(dst[i]);
+ SkPMColor resC = SkFastFourByteInterp256(src[i], dstC, scale);
+ if (a < 255) {
+ resC = SkFastFourByteInterp256(resC, dstC, a + (a >> 7));
+ }
+ dst[i] = SkPixel32ToPixel16(resC);
+ }
+ }
+ } else {
+ for (int i = 0; i < count; ++i) {
+ SkPMColor dstC = SkPixel16ToPixel32(dst[i]);
+ SkPMColor resC = SkFastFourByteInterp256(src[i], dstC, scale);
+ dst[i] = SkPixel32ToPixel16(resC);
+ }
+ }
+}
+
+void SkLerpXfermode::xferA8(SkAlpha dst[], const SkPMColor src[], int count,
+ const SkAlpha aa[]) const {
+ const int scale = fScale256;
+
+ if (aa) {
+ for (int i = 0; i < count; ++i) {
+ unsigned a = aa[i];
+ if (a) {
+ unsigned dstA = dst[i];
+ unsigned resA = SkAlphaBlend(SkGetPackedA32(src[i]), dstA, scale);
+ if (a < 255) {
+ resA = SkAlphaBlend(resA, dstA, a + (a >> 7));
+ }
+ dst[i] = resA;
+ }
+ }
+ } else {
+ for (int i = 0; i < count; ++i) {
+ dst[i] = SkAlphaBlend(SkGetPackedA32(src[i]), dst[i], scale);
+ }
+ }
+}
+
+#ifdef SK_DEVELOPER
+void SkLerpXfermode::toString(SkString* str) const {
+ str->printf("SkLerpXfermode: scale: %g", fScale256 / 256.0);
+}
+#endif