API to support native scaling by image-generator

BUG=skia:

Review URL: https://codereview.chromium.org/1396323007

2 files changed, 68 insertions, 0 deletions

diff --git a/src/core/SkImageGenerator.cpp b/src/core/SkImageGenerator.cpp
index 5e401920cd..dcd3ad00b1 100644
--- a/src/core/SkImageGenerator.cpp
+++ b/src/core/SkImageGenerator.cpp
@@ -111,6 +111,30 @@ GrTexture* SkImageGenerator::generateTexture(GrContext* ctx, const SkIRect* subs
     return this->onGenerateTexture(ctx, subset);
 }
 
+bool SkImageGenerator::computeScaledDimensions(SkScalar scale, SupportedSizes* sizes) {
+    if (scale > 0 && scale <= 1) {
+        return this->onComputeScaledDimensions(scale, sizes);
+    }
+    return false;
+}
+
+bool SkImageGenerator::generateScaledPixels(const SkISize& scaledSize,
+                                            const SkIPoint& subsetOrigin,
+                                            const SkPixmap& subsetPixels) {
+    if (scaledSize.width() <= 0 || scaledSize.height() <= 0) {
+        return false;
+    }
+    if (subsetPixels.width() <= 0 || subsetPixels.height() <= 0) {
+        return false;
+    }
+    const SkIRect subset = SkIRect::MakeXYWH(subsetOrigin.x(), subsetOrigin.y(),
+                                             subsetPixels.width(), subsetPixels.height());
+    if (!SkIRect::MakeWH(scaledSize.width(), scaledSize.height()).contains(subset)) {
+        return false;
+    }
+    return this->onGenerateScaledPixels(scaledSize, subsetOrigin, subsetPixels);
+}
+
 /////////////////////////////////////////////////////////////////////////////////////////////
 
 SkData* SkImageGenerator::onRefEncodedData() {
diff --git a/src/core/SkPictureImageGenerator.cpp b/src/core/SkPictureImageGenerator.cpp
index 556015d99e..39caa55d0c 100644
--- a/src/core/SkPictureImageGenerator.cpp
+++ b/src/core/SkPictureImageGenerator.cpp
@@ -21,6 +21,9 @@ public:
 protected:
     bool onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes, SkPMColor ctable[],
                      int* ctableCount) override;
+    bool onComputeScaledDimensions(SkScalar scale, SupportedSizes*) override;
+    bool onGenerateScaledPixels(const SkISize&, const SkIPoint&, const SkPixmap&) override;
+
 #if SK_SUPPORT_GPU
     GrTexture* onGenerateTexture(GrContext*, const SkIRect*) override;
 #endif
@@ -78,6 +81,47 @@ bool SkPictureImageGenerator::onGetPixels(const SkImageInfo& info, void* pixels,
     return true;
 }
 
+bool SkPictureImageGenerator::onComputeScaledDimensions(SkScalar scale,
+                                                        SupportedSizes* sizes) {
+    SkASSERT(scale > 0 && scale <= 1);
+    const int w = this->getInfo().width();
+    const int h = this->getInfo().height();
+    const int sw = SkScalarRoundToInt(scale * w);
+    const int sh = SkScalarRoundToInt(scale * h);
+    if (sw > 0 && sh > 0) {
+        sizes->fSizes[0].set(sw, sh);
+        sizes->fSizes[1].set(sw, sh);
+        return true;
+    }
+    return false;
+}
+
+bool SkPictureImageGenerator::onGenerateScaledPixels(const SkISize& scaledSize,
+                                                     const SkIPoint& scaledOrigin,
+                                                     const SkPixmap& scaledPixels) {
+    int w = scaledSize.width();
+    int h = scaledSize.height();
+
+    const SkScalar scaleX = SkIntToScalar(w) / this->getInfo().width();
+    const SkScalar scaleY = SkIntToScalar(h) / this->getInfo().height();
+    SkMatrix matrix = SkMatrix::MakeScale(scaleX, scaleY);
+    matrix.postTranslate(-SkIntToScalar(scaledOrigin.x()), -SkIntToScalar(scaledOrigin.y()));
+
+    SkBitmap bitmap;
+    if (!bitmap.installPixels(scaledPixels.info(), scaledPixels.writable_addr(),
+                              scaledPixels.rowBytes())) {
+        return false;
+    }
+
+    bitmap.eraseColor(SK_ColorTRANSPARENT);
+    SkCanvas canvas(bitmap, SkSurfaceProps(0, kUnknown_SkPixelGeometry));
+    matrix.preConcat(fMatrix);
+    canvas.drawPicture(fPicture, &matrix, fPaint.getMaybeNull());
+    return true;
+}
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
 SkImageGenerator* SkImageGenerator::NewFromPicture(const SkISize& size, const SkPicture* picture,
                                                    const SkMatrix* matrix, const SkPaint* paint) {
     return SkPictureImageGenerator::Create(size, picture, matrix, paint);