API and test for retrieving image filters from image objects

Added FPDFImageObj_GetImageFilterCount() and
FPDFImageObj_GetImageFilters() for retrieving image filters of image
objects.
    * Added a corresponding embedder test.
    * Changed the filter of an image object in embedded_image.pdf from
      DCTDecode to ASCIIHexDecode + DCTDecode, so we have a test case
      for images with more than one filter.

Bug=pdfium:677

Change-Id: I398790a2cad33fea4ca16a0eb0889c04caa6b962
Reviewed-on: https://pdfium-review.googlesource.com/10130
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Jane Liu <janeliulwq@google.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/fpdfsdk/fpdfeditimg.cpp b/fpdfsdk/fpdfeditimg.cpp
index 0d0c54604b..b4254e97c6 100644
--- a/fpdfsdk/fpdfeditimg.cpp
+++ b/fpdfsdk/fpdfeditimg.cpp
@@ -10,6 +10,8 @@
 #include "core/fpdfapi/page/cpdf_image.h"
 #include "core/fpdfapi/page/cpdf_imageobject.h"
 #include "core/fpdfapi/page/cpdf_pageobject.h"
+#include "core/fpdfapi/parser/cpdf_array.h"
+#include "core/fpdfapi/parser/cpdf_name.h"
 #include "fpdfsdk/fsdk_define.h"
 #include "third_party/base/ptr_util.h"
 
@@ -179,3 +181,46 @@ FPDFImageObj_GetImageDataRaw(FPDF_PAGEOBJECT image_object,
 
   return len;
 }
+
+DLLEXPORT int STDCALL
+FPDFImageObj_GetImageFilterCount(FPDF_PAGEOBJECT image_object) {
+  CPDF_PageObject* pObj = CPDFPageObjectFromFPDFPageObject(image_object);
+  if (!pObj || !pObj->IsImage())
+    return 0;
+
+  CFX_RetainPtr<CPDF_Image> pImg = pObj->AsImage()->GetImage();
+  if (!pImg)
+    return 0;
+
+  CPDF_Dictionary* pDict = pImg->GetDict();
+  CPDF_Object* pFilter = pDict ? pDict->GetDirectObjectFor("Filter") : nullptr;
+  if (!pFilter)
+    return 0;
+
+  if (pFilter->IsArray())
+    return pFilter->AsArray()->GetCount();
+  if (pFilter->IsName())
+    return 1;
+
+  return 0;
+}
+
+DLLEXPORT unsigned long STDCALL
+FPDFImageObj_GetImageFilter(FPDF_PAGEOBJECT image_object,
+                            int index,
+                            void* buffer,
+                            unsigned long buflen) {
+  if (index < 0 || index >= FPDFImageObj_GetImageFilterCount(image_object))
+    return 0;
+
+  CPDF_PageObject* pObj = CPDFPageObjectFromFPDFPageObject(image_object);
+  CPDF_Object* pFilter =
+      pObj->AsImage()->GetImage()->GetDict()->GetDirectObjectFor("Filter");
+  CFX_WideString wsFilters;
+  if (pFilter->IsName())
+    wsFilters = pFilter->AsName()->GetUnicodeText();
+  else
+    wsFilters = pFilter->AsArray()->GetUnicodeTextAt(index);
+
+  return Utf16EncodeMaybeCopyAndReturnLength(wsFilters, buffer, buflen);
+}