Implemented transparent gradients

src/pdf/SkPDFFormXObject.cpp

Index: src/pdf/SkPDFFormXObject.cpp
diff --git a/src/pdf/SkPDFFormXObject.cpp b/src/pdf/SkPDFFormXObject.cpp
index f31b90b79c389be4c46952261f59de25b16921b3..8484d71a0952ad219dd003bac77fecbc971314dd 100644
--- a/src/pdf/SkPDFFormXObject.cpp
+++ b/src/pdf/SkPDFFormXObject.cpp
@@ -28,10 +28,8 @@ SkPDFFormXObject::SkPDFFormXObject(SkPDFDevice* device) {
     SkAutoTUnref<SkData> content(device->copyContentToData());
     setData(content.get());
 
-    insertName("Type", "XObject");
-    insertName("Subtype", "Form");
-    SkSafeUnref(this->insert("BBox", device->copyMediaBox()));
-    insert("Resources", resourceDict);
+    SkAutoTUnref<SkPDFArray> bboxArray(device->copyMediaBox());
+    init(NULL, resourceDict, bboxArray);
 
     // We invert the initial transform and apply that to the xobject so that
     // it doesn't get applied twice. We can't just undo it because it's
@@ -45,11 +43,41 @@ SkPDFFormXObject::SkPDFFormXObject(SkPDFDevice* device) {
         }
         insert("Matrix", SkPDFUtils::MatrixToArray(inverse))->unref();
     }
+}
+
+/**
+ * Creates a FormXObject from a content stream and associated resources.
+ */
+SkPDFFormXObject::SkPDFFormXObject(SkData* content, SkRect bbox,
+                                   SkPDFResourceDict* resourceDict) {
+    SkTSet<SkPDFObject*> emptySet;
+    resourceDict->getResources(emptySet, &fResources, false);
+
+    setData(content);
+
+    SkAutoTUnref<SkPDFArray> bboxArray(SkPDFUtils::RectToArray(bbox));
+    init("DeviceRGB", resourceDict, bboxArray);

[vandebo (ex-Chrome), 2013/07/11 22:22:23]

Is CS required here?  I think table 7.13 of the 1.4 pdf spec implies it is.  Is
that your reading as well?

After this goes in, we might want to look into how much work it would be to
generate a DeviceGray FormXObject and use that instead.

[ducky, 2013/07/12 03:40:00]

Yep, looks like it's required when in luminosity mode. I also tried omitting it,
and the results were not as expected.

As for DeviceGray, I just tried and it works with both poppler and Chrome. I'm
going to leave it as DeviceRGB for now, since while it works, it may not be
spec-compliant. A more detailed look at the spec will be required (later). The
current gradient code outputs RGB, right?

[vandebo (ex-Chrome), 2013/07/12 21:41:43]

Converting to DeviceGray would require changing the gradient code to output just
a single channel.  It may work, but it's probably detecting the mismatch and
ignoring the DeviceGray color space.

+}
+
+/**
+ * Common initialization code.
+ * Note that bbox is unreferenced here, so calling code does not need worry.
+ */
+void SkPDFFormXObject::init(const char colorSpace[],
+                            SkPDFDict* resourceDict, SkPDFArray* bbox) {
+    insertName("Type", "XObject");
+    insertName("Subtype", "Form");
+    insert("Resources", resourceDict);
+    insert("BBox", bbox);
 
     // Right now SkPDFFormXObject is only used for saveLayer, which implies
     // isolated blending.  Do this conditionally if that changes.
     SkAutoTUnref<SkPDFDict> group(new SkPDFDict("Group"));
     group->insertName("S", "Transparency");
+
+    if (colorSpace != NULL) {
+        group->insertName("CS", colorSpace);
+    }
     group->insert("I", new SkPDFBool(true))->unref();  // Isolated.
     insert("Group", group.get());
 }