Implement DPI for perspective bitmaps in PDF - we save the bitmap at the resolution requested.

src/pdf/SkPDFDevice.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkPDFDevice.h"
 
 #include "SkAnnotation.h"
@@ skipping 31 matching lines @@
     int upperBounds;
 
     bool operator==(const TypefaceFallbackData& b) const {
         return typeface == b.typeface &&
                lowerBounds == b.lowerBounds &&
                upperBounds == b.upperBounds;
     }
 };
 #endif
 
+#define DPI_FOR_RASTER_SCALE_ONE 72
+
 // Utility functions
 
 static void emit_pdf_color(SkColor color, SkWStream* result) {
     SkASSERT(SkColorGetA(color) == 0xFF);  // We handle alpha elsewhere.
     SkScalar colorMax = SkIntToScalar(0xFF);
     SkPDFScalar::Append(
             SkScalarDiv(SkIntToScalar(SkColorGetR(color)), colorMax), result);
     result->writeText(" ");
     SkPDFScalar::Append(
             SkScalarDiv(SkIntToScalar(SkColorGetG(color)), colorMax), result);
@@ skipping 1971 matching lines @@
                                      const SkPaint& paint) {
     SkMatrix matrix = origMatrix;
     SkRegion perspectiveBounds;
     const SkRegion* clipRegion = &origClipRegion;
     SkBitmap perspectiveBitmap;
     const SkBitmap* bitmap = &origBitmap;
     SkBitmap tmpSubsetBitmap;
 
     // Rasterize the bitmap using perspective in a new bitmap.
     if (origMatrix.hasPerspective()) {
+        if (fRasterDpi == 0) {
+            return;
+        }
         SkBitmap* subsetBitmap;
         if (srcRect) {
             if (!origBitmap.extractSubset(&tmpSubsetBitmap, *srcRect)) {
                return;
             }
             subsetBitmap = &tmpSubsetBitmap;
         } else {
             subsetBitmap = &tmpSubsetBitmap;
             *subsetBitmap = origBitmap;
         }
         srcRect = NULL;
 
         // Transform the bitmap in the new space.
         SkPath perspectiveOutline;
         perspectiveOutline.addRect(
                 SkRect::MakeWH(SkIntToScalar(subsetBitmap->width()),
                                SkIntToScalar(subsetBitmap->height())));
         perspectiveOutline.transform(origMatrix);
 
         // TODO(edisonn): perf - use current clip too.
         // Retrieve the bounds of the new shape.
         SkRect bounds = perspectiveOutline.getBounds();
+        float scaleX = sqrt(fRasterDpi / (float)DPI_FOR_RASTER_SCALE_ONE);

[vandebo (ex-Chrome), 2013/10/31 19:26:43]

I don't understand, why sqrt ?

[edisonn, 2013/10/31 19:49:31]

For some reason I was thinking DPI is "dots per square inch". But you are right,
it is "dots per inch" so I removed the sqrt.

+        float scaleY = scaleX;
 
-        // TODO(edisonn): add DPI settings. Currently 1 pixel/point, which does
-        // not look great, but it is not producing large PDFs.
+        scaleX *= SkScalarToFloat(fInitialTransform.getScaleX());
+        scaleY *= SkScalarToFloat(fInitialTransform.getScaleY());
+
+        scaleX = fabs(scaleX);
+        scaleY = fabs(scaleY);
 
         // TODO(edisonn): A better approach would be to use a bitmap shader
         // (in clamp mode) and draw a rect over the entire bounding box. Then
         // intersect perspectiveOutline 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.
 
-        perspectiveBitmap.setConfig(SkBitmap::kARGB_8888_Config,
-                                    SkScalarCeilToInt(bounds.width()),
-                                    SkScalarCeilToInt(bounds.height()));
+        perspectiveBitmap.setConfig(
+                SkBitmap::kARGB_8888_Config,
+                SkScalarCeilToInt(scaleX * bounds.width()),

[vandebo (ex-Chrome), 2013/10/31 19:26:43]

This makes the image bigger

[edisonn, 2013/10/31 19:49:31]

correct, when bitmap is put in perspective mode, it tries to preserve as much
signal as it can it can, up to the DPI requested. Pixels that are farther away,
will became smaller, and the larger image will accommodate them.

Please run the gm to see yourself.

out/Debug/gm -w ~/gm_force_persp_1000/ --useDocumentInsteadOfDevice
--forcePerspectiveMatrix --match ~scaled_tilemodes ~convexpaths ~clipped-bitmap
~xfermodes --pdfRasterDpi 10

vs

out/Debug/gm -w ~/gm_force_persp_1000/ --useDocumentInsteadOfDevice
--forcePerspectiveMatrix --match ~scaled_tilemodes ~convexpaths ~clipped-bitmap
~xfermodes --pdfRasterDpi 100

+                SkScalarCeilToInt(scaleY * bounds.height()));
         perspectiveBitmap.allocPixels();
         perspectiveBitmap.eraseColor(SK_ColorTRANSPARENT);
 
         SkBitmapDevice device(perspectiveBitmap);
         SkCanvas canvas(&device);
 
         SkScalar deltaX = bounds.left();
         SkScalar deltaY = bounds.top();
 
         SkMatrix offsetMatrix = origMatrix;
         offsetMatrix.postTranslate(-deltaX, -deltaY);
+        offsetMatrix.postScale(scaleX, scaleY);

[vandebo (ex-Chrome), 2013/10/31 19:26:43]

Then this draws it bigger.  Should this be 1/scaleX ?

[edisonn, 2013/10/31 19:49:31]

The gms just work, I guess the code is correct.

[vandebo (ex-Chrome), 2013/10/31 23:20:36]

After much effort, I understand.  Above makes the canvas big, this says to draw
big.

 
         // Translate the draw in the new canvas, so we perfectly fit the
         // shape in the bitmap.
         canvas.setMatrix(offsetMatrix);
 
         canvas.drawBitmap(*subsetBitmap, SkIntToScalar(0), SkIntToScalar(0));
 
         // Make sure the final bits are in the bitmap.
         canvas.flush();
 
-        // In the new space, we use the identity matrix translated.
-        matrix.setTranslate(deltaX, deltaY);
+        // In the new space, we use the identity matrix translated
+        // and scaled to reflect DPI.
+        matrix.setScale(1 / scaleX, 1 / scaleY);
+        matrix.postTranslate(deltaX, deltaY);
         perspectiveBounds.setRect(
                 SkIRect::MakeXYWH(SkScalarFloorToInt(bounds.x()),
                                   SkScalarFloorToInt(bounds.y()),
                                   SkScalarCeilToInt(bounds.width()),
                                   SkScalarCeilToInt(bounds.height())));
         clipRegion = &perspectiveBounds;
         srcRect = NULL;
         bitmap = &perspectiveBitmap;
     }
 
@@ skipping 26 matching lines @@
 }
 
 bool SkPDFDevice::onReadPixels(const SkBitmap& bitmap, int x, int y,
                                SkCanvas::Config8888) {
     return false;
 }
 
 bool SkPDFDevice::allowImageFilter(SkImageFilter*) {
     return false;
 }