add newImage API

src/image/SkImage.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkImageGenerator.h"
@@ skipping 76 matching lines @@
     }
     return as_IB(this)->onNewSurface(info, *props);
 }
 
 const char* SkImage::toString(SkString* str) const {
     str->appendf("image: (id:%d (%d, %d) %s)", this->uniqueID(), this->width(), this->height(),
                  this->isOpaque() ? "opaque" : "");
     return str->c_str();
 }
 
+SkImage* SkImage::newImage(int newWidth, int newHeight, const SkIRect* subset,
+                           SkFilterQuality quality) const {
+    if (newWidth < 0 || newHeight < 0) {
+        return NULL;
+    }
+    if (subset && !SkIRect::MakeWH(this->width(), this->height()).contains(*subset)) {
+        return NULL;
+    }
+
+    if (NULL == subset && this->width() == newWidth && this->height() == newHeight) {
+        return SkRef(const_cast<SkImage*>(this));
+    }
+
+    return as_IB(this)->onNewImage(newWidth, newHeight, subset, quality);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 static bool raster_canvas_supports(const SkImageInfo& info) {
     switch (info.colorType()) {
         case kN32_SkColorType:
             return kUnpremul_SkAlphaType != info.alphaType();
         case kRGB_565_SkColorType:
             return true;
         case kAlpha_8_SkColorType:
             return true;
@@ skipping 12 matching lines @@
     SkBitmap bm;
     bm.installPixels(dstInfo, dstPixels, dstRowBytes);
     SkCanvas canvas(bm);
 
     SkPaint paint;
     paint.setXfermodeMode(SkXfermode::kSrc_Mode);
     canvas.drawImage(this, -SkIntToScalar(srcX), -SkIntToScalar(srcY), &paint);
 
     return true;
 }
+
+SkImage* SkImage_Base::onNewImage(int newWidth, int newHeight, const SkIRect* subset,
+                                  SkFilterQuality quality) const {
+    const bool opaque = this->isOpaque();
+    const SkImageInfo info = SkImageInfo::Make(newWidth, newHeight, kN32_SkColorType,

[scroggo, 2015/01/21 22:24:57]

As discussed in person, we don't actually know the alpha type of this, so we
don't know whether we can draw in software....

+                                               opaque ? kOpaque_SkAlphaType : kPremul_SkAlphaType);
+    SkAutoTUnref<SkSurface> surface(this->newSurface(info, NULL));
+    if (!surface.get()) {
+        return NULL;
+    }
+
+    SkRect src;
+    if (subset) {
+        src.set(*subset);
+    } else {
+        src = SkRect::MakeWH(SkIntToScalar(this->width()), SkIntToScalar(this->height()));
+    }
+
+    surface->getCanvas()->scale(newWidth / src.width(), newHeight / src.height());
+    surface->getCanvas()->translate(-src.x(), -src.y());
+
+    SkPaint paint;
+    paint.setXfermodeMode(SkXfermode::kSrc_Mode);
+    paint.setFilterQuality(quality);
+    surface->getCanvas()->drawImage(this, 0, 0, &paint);
+    return surface->newImageSnapshot();
+}
+
+