Implement a generic matrix transform image filter.

src/effects/SkTransformImageFilter.cpp

+/*
+ * Copyright 2014 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.
+ */
+
+#include "SkTransformImageFilter.h"
+#include "SkBitmap.h"
+#include "SkCanvas.h"
+#include "SkDevice.h"
+#include "SkColorPriv.h"
+#include "SkReadBuffer.h"
+#include "SkWriteBuffer.h"
+#include "SkMatrix.h"
+#include "SkRect.h"
+
+SkTransformImageFilter::SkTransformImageFilter(const SkMatrix& transform,
+                                               SkPaint::FilterLevel filterLevel,
+                                               SkImageFilter* input)
+  : INHERITED(input),
+    fTransform(transform),
+    fFilterLevel(filterLevel) {
+}
+
+SkTransformImageFilter* SkTransformImageFilter::Create(const SkMatrix& transform,
+                                                       SkPaint::FilterLevel filterLevel,
+                                                       SkImageFilter* input) {
+    return SkNEW_ARGS(SkTransformImageFilter, (transform, filterLevel, input));
+}
+
+SkTransformImageFilter::SkTransformImageFilter(SkReadBuffer& buffer)
+  : INHERITED(1, buffer) {
+    buffer.readMatrix(&fTransform);
+    fFilterLevel = static_cast<SkPaint::FilterLevel>(buffer.readInt());
+}
+
+void SkTransformImageFilter::flatten(SkWriteBuffer& buffer) const {
+    this->INHERITED::flatten(buffer);
+    buffer.writeMatrix(fTransform);
+    buffer.writeInt(fFilterLevel);
+}
+
+SkTransformImageFilter::~SkTransformImageFilter() {
+}
+
+bool SkTransformImageFilter::onFilterImage(Proxy* proxy,
+                                           const SkBitmap& source,
+                                           const Context& ctx,
+                                           SkBitmap* result,
+                                           SkIPoint* offset) const {
+    SkBitmap src = source;
+    SkIPoint srcOffset = SkIPoint::Make(0, 0);
+    if (getInput(0) && !getInput(0)->filterImage(proxy, source, ctx, &src, &srcOffset)) {
+        return false;
+    }
+
+    SkRect dstRect;
+    SkIRect srcBounds, dstBounds;
+    src.getBounds(&srcBounds);
+    srcBounds.offset(srcOffset);
+    SkRect srcRect = SkRect::Make(srcBounds);
+    SkMatrix matrix;
+    if (!ctx.ctm().invert(&matrix)) {
+        return false;
+    }
+    matrix.postConcat(fTransform);
+    matrix.postConcat(ctx.ctm());
+    matrix.mapRect(&dstRect, srcRect);
+    dstRect.roundOut(&dstBounds);
+
+    SkAutoTUnref<SkBaseDevice> device(proxy->createDevice(dstBounds.width(), dstBounds.height()));
+    if (NULL == device.get()) {
+        return false;
+    }
+
+    SkCanvas canvas(device.get());
+    canvas.translate(-SkIntToScalar(dstBounds.x()), -SkIntToScalar(dstBounds.y()));
+    canvas.concat(matrix);
+    SkPaint paint;
+
+    paint.setXfermodeMode(SkXfermode::kSrc_Mode);
+    paint.setFilterLevel(fFilterLevel);
+    canvas.drawBitmap(src, srcRect.x(), srcRect.y(), &paint);
+
+    *result = device.get()->accessBitmap(false);
+    offset->fX = dstBounds.fLeft;
+    offset->fY = dstBounds.fTop;
+    return true;
+}
+
+void SkTransformImageFilter::computeFastBounds(const SkRect& src, SkRect* dst) const {
+    SkRect bounds = src;
+    if (getInput(0)) {
+        getInput(0)->computeFastBounds(src, &bounds);
+    }
+    SkMatrix matrix;
+    matrix.setTranslate(-bounds.x(), -bounds.y());
+    matrix.postConcat(fTransform);
+    matrix.postTranslate(bounds.x(), bounds.y());
+    matrix.mapRect(dst, bounds);
+}
+
+bool SkTransformImageFilter::onFilterBounds(const SkIRect& src, const SkMatrix& ctm,
+                                            SkIRect* dst) const {
+    SkMatrix transformInverse;
+    if (!fTransform.invert(&transformInverse)) {
+        return false;
+    }
+    SkMatrix matrix;
+    if (!ctm.invert(&matrix)) {
+        return false;
+    }
+    matrix.postConcat(transformInverse);
+    matrix.postConcat(ctm);
+    SkRect floatBounds;
+    matrix.mapRect(&floatBounds, SkRect::Make(src));
+    SkIRect bounds;
+    floatBounds.roundOut(&bounds);
+    if (getInput(0) && !getInput(0)->filterBounds(bounds, ctm, &bounds)) {
+        return false;
+    }
+
+    *dst = bounds;
+    return true;
+}