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, 46 insertions, 0 deletions

diff --git a/fpdfsdk/fpdfedit_embeddertest.cpp b/fpdfsdk/fpdfedit_embeddertest.cpp
index c381b25efa..e62ef2149b 100644
--- a/fpdfsdk/fpdfedit_embeddertest.cpp
+++ b/fpdfsdk/fpdfedit_embeddertest.cpp
@@ -1038,3 +1038,49 @@ TEST_F(FPDFEditEmbeddertest, DestroyPageObject) {
   // There should be no memory leaks with a call to FPDFPageObj_Destroy().
   FPDFPageObj_Destroy(rect);
 }
+
+TEST_F(FPDFEditEmbeddertest, GetImageFilters) {
+  EXPECT_TRUE(OpenDocument("embedded_images.pdf"));
+  FPDF_PAGE page = LoadPage(0);
+  ASSERT_TRUE(page);
+
+  // Verify that retrieving the filter of a non-image object would fail.
+  FPDF_PAGEOBJECT obj = FPDFPage_GetObject(page, 32);
+  ASSERT_NE(FPDF_PAGEOBJ_IMAGE, FPDFPageObj_GetType(obj));
+  ASSERT_EQ(0, FPDFImageObj_GetImageFilterCount(obj));
+  EXPECT_EQ(0u, FPDFImageObj_GetImageFilter(obj, 0, nullptr, 0));
+
+  // Verify the returned filter string for an image object with a single filter.
+  obj = FPDFPage_GetObject(page, 33);
+  ASSERT_EQ(FPDF_PAGEOBJ_IMAGE, FPDFPageObj_GetType(obj));
+  ASSERT_EQ(1, FPDFImageObj_GetImageFilterCount(obj));
+  unsigned long len = FPDFImageObj_GetImageFilter(obj, 0, nullptr, 0);
+  std::vector<char> buf(len);
+  EXPECT_EQ(24u, FPDFImageObj_GetImageFilter(obj, 0, buf.data(), len));
+  EXPECT_STREQ(L"FlateDecode",
+               GetPlatformWString(reinterpret_cast<unsigned short*>(buf.data()))
+                   .c_str());
+  EXPECT_EQ(0u, FPDFImageObj_GetImageFilter(obj, 1, nullptr, 0));
+
+  // Verify all the filters for an image object with a list of filters.
+  obj = FPDFPage_GetObject(page, 38);
+  ASSERT_EQ(FPDF_PAGEOBJ_IMAGE, FPDFPageObj_GetType(obj));
+  ASSERT_EQ(2, FPDFImageObj_GetImageFilterCount(obj));
+  len = FPDFImageObj_GetImageFilter(obj, 0, nullptr, 0);
+  buf.clear();
+  buf.resize(len);
+  EXPECT_EQ(30u, FPDFImageObj_GetImageFilter(obj, 0, buf.data(), len));
+  EXPECT_STREQ(L"ASCIIHexDecode",
+               GetPlatformWString(reinterpret_cast<unsigned short*>(buf.data()))
+                   .c_str());
+
+  len = FPDFImageObj_GetImageFilter(obj, 1, nullptr, 0);
+  buf.clear();
+  buf.resize(len);
+  EXPECT_EQ(20u, FPDFImageObj_GetImageFilter(obj, 1, buf.data(), len));
+  EXPECT_STREQ(L"DCTDecode",
+               GetPlatformWString(reinterpret_cast<unsigned short*>(buf.data()))
+                   .c_str());
+
+  UnloadPage(page);
+}