flesh out gradient shaders

Using these webpages as guides

  http://www.globelegislators.org/pdfjs/test/pdfs/alphatrans.pdf

  http://www.antennahouse.com/antenna1/wp-content/uploads/2015/07/background-image-gradient-1.pdf

flesh out the gradient shaders to include the PostScript Type 0
sampling function and to include radial gradients. This CL makes
rendering these pages agree with Adobe Reader output.

Some of these examples use an Extend array to clip the gradient.
Skia does not currently support this natively, so construct the
clip manually for now.

Other PDF pages may construct gradients using alternate mechanisms
-- this code will continue to be refactored as those come to light.

In particular, this CL sets up the clip and matrix differently for
axial gradients and radial gradients -- while it makes sense to do
it one way only, I prefer to defer until I have more examples to
work with.

R=dsinclair@chromium.org,tsepez@chromium.org

Review URL: https://codereview.chromium.org/1870463002

1 files changed, 28 insertions, 0 deletions

diff --git a/core/fpdfapi/fpdf_page/pageint.h b/core/fpdfapi/fpdf_page/pageint.h
index e6496cfd20..98a05d5495 100644
--- a/core/fpdfapi/fpdf_page/pageint.h
+++ b/core/fpdfapi/fpdf_page/pageint.h
@@ -393,6 +393,7 @@ class CPDF_Function {
   uint32_t CountInputs() const { return m_nInputs; }
   uint32_t CountOutputs() const { return m_nOutputs; }
   FX_FLOAT GetDomain(int i) const { return m_pDomains[i]; }
+  FX_FLOAT GetRange(int i) const { return m_pRanges[i]; }
   Type GetType() const { return m_Type; }
 
  protected:
@@ -423,6 +424,33 @@ class CPDF_ExpIntFunc : public CPDF_Function {
   FX_FLOAT* m_pEndValues;
 };
 
+class CPDF_SampledFunc : public CPDF_Function {
+ public:
+  struct SampleEncodeInfo {
+    FX_FLOAT encode_max;
+    FX_FLOAT encode_min;
+    uint32_t sizes;
+  };
+
+  struct SampleDecodeInfo {
+    FX_FLOAT decode_max;
+    FX_FLOAT decode_min;
+  };
+
+  CPDF_SampledFunc();
+  ~CPDF_SampledFunc() override;
+
+  // CPDF_Function
+  FX_BOOL v_Init(CPDF_Object* pObj) override;
+  FX_BOOL v_Call(FX_FLOAT* inputs, FX_FLOAT* results) const override;
+
+  SampleEncodeInfo* m_pEncodeInfo;
+  SampleDecodeInfo* m_pDecodeInfo;
+  uint32_t m_nBitsPerSample;
+  uint32_t m_SampleMax;
+  CPDF_StreamAcc* m_pSampleStream;
+};
+
 class CPDF_StitchFunc : public CPDF_Function {
  public:
   CPDF_StitchFunc();