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

src/pdf/SkPDFDevice.cpp

Index: src/pdf/SkPDFDevice.cpp
diff --git a/src/pdf/SkPDFDevice.cpp b/src/pdf/SkPDFDevice.cpp
index a7d2bd459accb39c70518ef21afc1289b30d3723..c97e022a386e9593dfd1c46cfdc5cd37d36d5ec9 100644
--- a/src/pdf/SkPDFDevice.cpp
+++ b/src/pdf/SkPDFDevice.cpp
@@ -49,6 +49,8 @@ struct TypefaceFallbackData {
 };
 #endif
 
+#define DPI_FOR_RASTER_SCALE_ONE 72
+
 // Utility functions
 
 static void emit_pdf_color(SkColor color, SkWStream* result) {
@@ -2040,6 +2042,9 @@ void SkPDFDevice::internalDrawBitmap(const SkMatrix& origMatrix,
 
     // 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)) {
@@ -2062,9 +2067,14 @@ void SkPDFDevice::internalDrawBitmap(const SkMatrix& 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;
+
+        scaleX *= SkScalarToFloat(fInitialTransform.getScaleX());
+        scaleY *= SkScalarToFloat(fInitialTransform.getScaleY());
 
-        // TODO(edisonn): add DPI settings. Currently 1 pixel/point, which does
-        // not look great, but it is not producing large PDFs.
+        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
@@ -2073,9 +2083,10 @@ void SkPDFDevice::internalDrawBitmap(const SkMatrix& origMatrix,
         // 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);
 
@@ -2087,6 +2098,7 @@ void SkPDFDevice::internalDrawBitmap(const SkMatrix& origMatrix,
 
         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.
@@ -2097,8 +2109,10 @@ void SkPDFDevice::internalDrawBitmap(const SkMatrix& origMatrix,
         // 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()),