PDF: Properly apply the CropBox to the MediaBox.

pdf/pdfium/pdfium_engine.cc

 // Copyright (c) 2012 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.
 
 #include "pdf/pdfium/pdfium_engine.h"
 
 #include <math.h>
 
 #include "base/i18n/icu_encoding_detection.h"
 #include "base/i18n/icu_string_conversions.h"
@@ skipping 80 matching lines @@
 // than the above to keep things smooth if the user is scrolling quickly. We
 // try painting a little because with accelerated compositing, we get flushes
 // only every 16 ms. If we were to wait until the next flush to paint the rest
 // of the pdf, we would never get to draw the pdf and would only draw the
 // scrollbars. This value is picked to give enough time for gpu related code to
 // do its thing and still fit within the timelimit for 60Hz. For the
 // non-composited case, this doesn't make things worse since we're still
 // painting the scrollbars > 60 Hz.
 #define kMaxInitialProgressivePaintTimeMs 10
 
-struct ClipBox {
-  float left;
-  float right;
-  float top;
-  float bottom;
-};
-
 std::vector<uint32_t> GetPageNumbersFromPrintPageNumberRange(
     const PP_PrintPageNumberRange_Dev* page_ranges,
     uint32_t page_range_count) {
   std::vector<uint32_t> page_numbers;
   for (uint32_t index = 0; index < page_range_count; ++index) {
     for (uint32_t page_number = page_ranges[index].first_page_number;
          page_number <= page_ranges[index].last_page_number; ++page_number) {
       page_numbers.push_back(page_number);
     }
   }
@@ skipping 231 matching lines @@
 
   double actual_source_page_width = rotated ? src_height : src_width;
   double actual_source_page_height = rotated ? src_width : src_height;
   double ratio_x = static_cast<double>(content_rect.width()) /
                    actual_source_page_width;
   double ratio_y = static_cast<double>(content_rect.height()) /
                    actual_source_page_height;
   return std::min(ratio_x, ratio_y);
 }
 
+// A rect struct for use with FPDF bounding box functions.
+// Remember with PDFs, origin is bottom-left.

[raymes, 2015/10/01 04:19:48]

nit: fill 80chars

[Lei Zhang, 2015/10/01 04:50:03]

I did this on purpose since it takes 2 lines anyway.

+struct ClipBox {
+  float left;
+  float right;
+  float top;
+  float bottom;
+};
+
+// Make the default size to be letter size (8.5" X 11"). We are just following
+// the PDFium way of handling these corner cases. PDFium always consider
+// US-Letter as the default page size.
+void SetDefaultClipBox(bool rotated, ClipBox* clip_box) {
+  const int kDpi = 72;
+  const float kPaperWidth = 8.5 * kDpi;
+  const float kPaperHeight = 11 * kDpi;
+  clip_box->left = 0;
+  clip_box->bottom = 0;
+  clip_box->right = rotated ? kPaperHeight : kPaperWidth;
+  clip_box->top = rotated ? kPaperWidth : kPaperHeight;
+}
+
 // Compute source clip box boundaries based on the crop box / media box of
 // source page and scale factor.
 //
 // |page| Handle to the source page. Returned by FPDF_LoadPage function.
 // |scale_factor| specifies the scale factor that should be applied to source
 // clip box boundaries.
 // |rotated| True if source page is rotated 90 degree or 270 degree.
 // |clip_box| out param to hold the computed source clip box values.
 void CalculateClipBoxBoundary(FPDF_PAGE page, double scale_factor, bool rotated,
                               ClipBox* clip_box) {
-  if (!FPDFPage_GetCropBox(page, &clip_box->left, &clip_box->bottom,
-                           &clip_box->right, &clip_box->top)) {
-    if (!FPDFPage_GetMediaBox(page, &clip_box->left, &clip_box->bottom,
-                              &clip_box->right, &clip_box->top)) {
-      // Make the default size to be letter size (8.5" X 11"). We are just
-      // following the PDFium way of handling these corner cases. PDFium always
-      // consider US-Letter as the default page size.
-      float paper_width = 612;
-      float paper_height = 792;
-      clip_box->left = 0;
-      clip_box->bottom = 0;
-      clip_box->right = rotated ? paper_height : paper_width;
-      clip_box->top = rotated ? paper_width : paper_height;
-    }
+  ClipBox media_box;
+  if (!FPDFPage_GetMediaBox(page, &media_box.left, &media_box.bottom,
+                            &media_box.right, &media_box.top)) {
+    SetDefaultClipBox(rotated, &media_box);
   }
+
+  ClipBox crop_box;
+  if (!FPDFPage_GetCropBox(page, &crop_box.left, &crop_box.bottom,
+                          &crop_box.right, &crop_box.top)) {
+    SetDefaultClipBox(rotated, &crop_box);
+  }
+
+  // Clip |media_box| to the size of |crop_box|, but ignore |crop_box| if it is
+  // bigger than |media_box|.
+  clip_box->left =
+      (crop_box.left < media_box.left) ? media_box.left : crop_box.left;
+  clip_box->right =
+      (crop_box.right > media_box.right) ? media_box.right : crop_box.right;
+  clip_box->top = (crop_box.top > media_box.top) ? media_box.top : crop_box.top;
+  clip_box->bottom =
+      (crop_box.bottom < media_box.bottom) ? media_box.bottom : crop_box.bottom;
+
+  // Finally, scale |clip_box|.
   clip_box->left *= scale_factor;
   clip_box->right *= scale_factor;
   clip_box->bottom *= scale_factor;
   clip_box->top *= scale_factor;
 }
 
 // Calculate the clip box translation offset for a page that does need to be
 // scaled. All parameters are in points.
 //
 // |content_rect| specifies the printable area of the destination page, with
@@ skipping 3668 matching lines @@
     double* height) {
   FPDF_DOCUMENT doc = FPDF_LoadMemDocument(pdf_buffer, pdf_buffer_size, NULL);
   if (!doc)
     return false;
   bool success = FPDF_GetPageSizeByIndex(doc, page_number, width, height) != 0;
   FPDF_CloseDocument(doc);
   return success;
 }
 
 }  // namespace chrome_pdf