Implement PrintPageAsJPEG feature for Print Preview

src/chrome/renderer/print_web_view_helper.cc

Index: src/chrome/renderer/print_web_view_helper.cc
===================================================================
--- src/chrome/renderer/print_web_view_helper.cc	(revision 25428)
+++ src/chrome/renderer/print_web_view_helper.cc	(working copy)
@@ -5,6 +5,7 @@
 #include "chrome/renderer/print_web_view_helper.h"
 
 #include "app/l10n_util.h"
+#include "base/gfx/jpeg_codec.h"
 #include "base/logging.h"
 #include "chrome/common/render_messages.h"
 #include "chrome/renderer/render_view.h"
@@ -139,6 +140,41 @@
   }
 }
 
+void PrintWebViewHelper::PrintPageAsJPEG(
+    const ViewMsg_PrintPage_Params& params,
+    WebFrame* frame,
+    float zoom_factor,
+    std::vector<unsigned char>* image_data) {
+  PrepareFrameAndViewForPrint prep_frame_view(params.params,
+                                              frame,
+                                              frame->view());
+  const gfx::Size& canvas_size(prep_frame_view.GetPrintCanvasSize());
+
+  // Since WebKit extends the page width depending on the magical shrink
+  // factor we make sure the canvas covers the worst case scenario
+  // (x2.0 currently).  PrintContext will then set the correct clipping region.
+  int size_x = static_cast<int>(canvas_size.width() * params.params.max_shrink);
+  int size_y = static_cast<int>(canvas_size.height() *
+      params.params.max_shrink);
+
+  // Access the bitmap from the canvas device.
+  skia::PlatformCanvas canvas(size_x, size_y, true);
+  frame->printPage(params.page_number, &canvas);
+  const SkBitmap& bitmap = canvas.getDevice()->accessBitmap(false);
+
+  // Encode the SkBitmap to jpeg.
+  SkAutoLockPixels image_lock(bitmap);
+  bool encoded = JPEGCodec::Encode(
+      reinterpret_cast<unsigned char*>(bitmap.getAddr32(0, 0)),
+      JPEGCodec::FORMAT_BGRA,
+      static_cast<int>(bitmap.width() * zoom_factor),
+      static_cast<int>(bitmap.height() * zoom_factor),
+      static_cast<int>(bitmap.rowBytes()),
+      90,
+      image_data);
+  DCHECK(encoded);
+}
+
 bool PrintWebViewHelper::Send(IPC::Message* msg) {
   return render_view_->Send(msg);
 }