Implement PrintPageAsJPEG feature for Print Preview

src/chrome/renderer/print_web_view_helper.h

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_RENDERER_PRINT_WEB_VIEW_DELEGATE_H_
 #define CHROME_RENDERER_PRINT_WEB_VIEW_DELEGATE_H_
 
 #include <vector>
 
 #include "base/gfx/size.h"
@@ skipping 57 matching lines @@
   void Print(WebKit::WebFrame* frame, bool script_initiated);
 
   // Is there a background print in progress?
   bool IsPrinting() {
     return print_web_view_.get() != NULL;
   }
 
   // Notification when printing is done - signal teardown
   void DidFinishPrinting(bool success);
 
+  // Prints the page listed in |params| as a JPEG image. The width and height of
+  // the image will scale propotionally given the |zoom_factor| multiplier. The
+  // encoded JPEG data will be written into the supplied vector |image_data|.
+  void PrintPageAsJPEG(const ViewMsg_PrintPage_Params& params,
+                       WebKit::WebFrame* frame,
+                       float zoom_factor,
+                       std::vector<unsigned char>* image_data);
+
  protected:
   bool CopyAndPrint(const ViewMsg_PrintPages_Params& params,
                     WebKit::WebFrame* web_frame);
 
   // Prints the page listed in |params|.
   void PrintPage(const ViewMsg_PrintPage_Params& params,
                  const gfx::Size& canvas_size,
                  WebKit::WebFrame* frame);
 
   // Prints all the pages listed in |params|.
@@ skipping 27 matching lines @@
   scoped_ptr<WebView> print_web_view_;
   scoped_ptr<ViewMsg_PrintPages_Params> print_pages_params_;
   base::Time last_cancelled_script_print_;
   int user_cancelled_scripted_print_count_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PrintWebViewHelper);
 };
 
 #endif  // CHROME_RENDERER_PRINT_WEB_VIEW_DELEGATE_H_