Implement perspective for bitmaps in pdf.

src/pdf/SkPDFDevice.cpp

Index: src/pdf/SkPDFDevice.cpp
diff --git a/src/pdf/SkPDFDevice.cpp b/src/pdf/SkPDFDevice.cpp
index 43117a2b2fc4d5760d692cb50970070721d71b0c..d4bb2b64a5854a8a611b43462deba29389d8f1cf 100644
--- a/src/pdf/SkPDFDevice.cpp
+++ b/src/pdf/SkPDFDevice.cpp
@@ -2028,13 +2028,82 @@ int SkPDFDevice::getFontResourceIndex(SkTypeface* typeface, uint16_t glyphID) {
     return resourceIndex;
 }
 
-void SkPDFDevice::internalDrawBitmap(const SkMatrix& matrix,
+static void setup_transparent_bitmap(SkBitmap* bitmap, int width, int height) {
+    bitmap->setConfig(SkBitmap::kARGB_8888_Config, width, height);
+    bitmap->allocPixels();
+    bitmap->eraseColor(SK_ColorTRANSPARENT);
+}
+
+void SkPDFDevice::internalDrawBitmap(const SkMatrix& origMatrix,
                                      const SkClipStack* clipStack,
-                                     const SkRegion& clipRegion,
-                                     const SkBitmap& bitmap,
-                                     const SkIRect* srcRect,
+                                     const SkRegion& origClipRegion,
+                                     const SkBitmap& origBitmap,
+                                     const SkIRect* origSrcRect,
                                      const SkPaint& paint) {
-    // TODO(edisonn): Perspective matrix support implemented here
+    SkMatrix matrix = origMatrix;
+    SkRegion all;

[vandebo (ex-Chrome), 2013/10/15 21:41:32]

nit: all -> perspectiveBounds ?

[edisonn, 2013/10/16 15:08:03]

Done.

+    const SkRegion* clipRegion = &origClipRegion;
+    SkBitmap subsetBitmap = origBitmap;

[vandebo (ex-Chrome), 2013/10/15 21:41:32]

nit: Pull inside the hasPerspective if on 2051 and make it a pointer to avoid an
unneeded copy.

[edisonn, 2013/10/16 15:08:03]

Done.

+    SkBitmap bitmap = origBitmap;

[vandebo (ex-Chrome), 2013/10/15 21:41:32]

For both the perspective and non-perspective case this makes an unneeded copy. 
Maybe make bitmap a pointer and point at origBitmap or a local
perspectiveBitmap?

[edisonn, 2013/10/16 15:08:03]

Done.

+    const SkIRect* srcRect = origSrcRect;

[vandebo (ex-Chrome), 2013/10/15 21:41:32]

not needed, just reset origSrcRect to NULL if you apply it.

[edisonn, 2013/10/16 15:08:03]

Done.

+
+    // Raster the bitmap using perspective in a new bitmap.
+    if (matrix.hasPerspective()) {

[vandebo (ex-Chrome), 2013/10/15 21:41:32]

nit: use origMatrix in this code block (except where you set matrix at the end).
It'll make it more clear that you're dealing with origMatrix and not something
you've computed and put into matrix.

[edisonn, 2013/10/16 15:08:03]

Done.

+        if (origSrcRect) {
+            if (!origBitmap.extractSubset(&subsetBitmap, *origSrcRect)) {
+               return;
+            }
+        } else {
+            subsetBitmap = origBitmap;
+        }
+        srcRect = NULL;
+
+        // Transform the bitmap in the new space.
+        SkPath path;

[vandebo (ex-Chrome), 2013/10/15 21:41:32]

nit: path -> perspectiveOutline ?

[edisonn, 2013/10/16 15:08:03]

Done.

+        path.addRect(SkRect::MakeWH(SkIntToScalar(subsetBitmap.width()),
+                                    SkIntToScalar(subsetBitmap.height())));
+        path.transform(matrix);
+
+        // Retrieve the bounds of the new shape.
+        SkRect bounds = path.getBounds();
+
+        // TODO(edisonn): add DPI settings. Currently 1 pixel/point, which does not look great,

[vandebo (ex-Chrome), 2013/10/15 21:41:32]

Nothing to be done, but this isn't necessarily 72 DPI, it depends on matrix.

+        // but it is not producing large PDFs.
+
+        // Create transparent bitmap.
+        setup_transparent_bitmap(&bitmap, bounds.width(), bounds.height());

[vandebo (ex-Chrome), 2013/10/15 21:41:32]

This approach looks fine and could be committed this way.  I think a better
approach would be to use a bitmap shader (in clamp mode) and draw a rect over
the entire bounding box.  Then intersect path from 2062 to the clip.  That will
avoid introducing alpha to the image while still giving good behavior at the
edge of the image.  Avoiding alpha will reduce the pdf size and generation CPU
time some.

[edisonn, 2013/10/16 15:08:03]

Added a todo, will keep the code as is
On 2013/10/15 21:41:32, vandebo wrote:

+
+        SkAutoTUnref<SkBitmapDevice> device(SkNEW_ARGS(SkBitmapDevice, (bitmap)));

[vandebo (ex-Chrome), 2013/10/15 21:41:32]

Why not stack allocate this?

[edisonn, 2013/10/16 15:08:03]

Done.

+        SkCanvas canvas(device);
+
+        // Find where (0,0) gets mapped in the new space.
+        SkPoint zeroZero = SkPoint::Make(SkIntToScalar(0), SkIntToScalar(0));
+        matrix.mapPoints(&zeroZero, 1);
+
+        SkScalar deltaX = bounds.left();
+        SkScalar deltaY = bounds.top();
+
+        SkMatrix matrix2 = matrix;

[vandebo (ex-Chrome), 2013/10/15 21:41:32]

nit: matrix2 -> offsetMatrix ?

[edisonn, 2013/10/16 15:08:03]

Done.

+        matrix2.postTranslate(-deltaX, -deltaY);
+
+        // Translate the draw in the new canvas, so we perfectly fit the shape in the bitmap.
+        canvas.setMatrix(matrix2);
+
+        canvas.drawBitmap(subsetBitmap, SkIntToScalar(0), SkIntToScalar(0));
+
+        // Make sure the final bits ar in the bitmap.
+        canvas.flush();
+
+        // In the new space, we use the identity matrix translated.
+        matrix.setTranslate(deltaX, deltaY);
+        all.setRect(SkIRect::MakeXYWH(SkScalarToFixed(bounds.x()),
+                                      SkScalarToFixed(bounds.y()),
+                                      SkScalarToFixed(bounds.width()),
+                                      SkScalarToFixed(bounds.height())));
+        clipRegion = &all;
+        srcRect = NULL;
+    }
+
     SkMatrix scaled;
     // Adjust for origin flip.
     scaled.setScale(SK_Scalar1, -SK_Scalar1);
@@ -2044,7 +2113,8 @@ void SkPDFDevice::internalDrawBitmap(const SkMatrix& matrix,
     scaled.postScale(SkIntToScalar(subset.width()),
                      SkIntToScalar(subset.height()));
     scaled.postConcat(matrix);
-    ScopedContentEntry content(this, clipStack, clipRegion, scaled, paint);
+
+    ScopedContentEntry content(this, clipStack, *clipRegion, scaled, paint);
     if (!content.entry()) {
         return;
     }