SkPdf: smaller color serialization

SkPDFUtils now has a special function (SkPDFUtils::AppendColorComponent)
just for writing out (color/255) as a decimal with three digits of
precision.

SkPDFUnion now has a type to represent a color component.  It holds a
utint_8, but calls into AppendColorComponent to serialize.

Added a unit test that tests all possible input values.
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2151863003

Review-Url: https://codereview.chromium.org/2151863003

1 files changed, 13 insertions, 0 deletions

diff --git a/tests/PDFPrimitivesTest.cpp b/tests/PDFPrimitivesTest.cpp
index 9e2a89e609..d816b60823 100644
--- a/tests/PDFPrimitivesTest.cpp
+++ b/tests/PDFPrimitivesTest.cpp
@@ -491,3 +491,16 @@ DEF_TEST(PDFPrimitives_Scalar, reporter) {
         check_pdf_scalar_serialization(reporter, inputFloat);
     }
 }
+
+// Test SkPDFUtils:: for accuracy.
+DEF_TEST(PDFPrimitives_Color, reporter) {
+    char buffer[5];
+    for (int i = 0; i < 256; ++i) {
+        size_t len = SkPDFUtils::ColorToDecimal(i, buffer);
+        REPORTER_ASSERT(reporter, len == strlen(buffer));
+        float f;
+        REPORTER_ASSERT(reporter, 1 == sscanf(buffer, "%f", &f));
+        int roundTrip = (int)(0.5 + f * 255);
+        REPORTER_ASSERT(reporter, roundTrip == i);
+    }
+}