commit 5c41f3676effd563cb610a24f3b30cae0adabaf8
author Hal Canary <halcanary@google.com> Mon Sep 30 10:54:54 2019 -0400
committer Skia Commit-Bot <skia-commit-bot@chromium.org> Mon Sep 30 16:56:48 2019 +0000
tree e58fec40a36f9730855019b80cfdf9d93646c5f4
parent 729fc0cb65f72bfd70ff9f09a404d2d5da8716f2

SkPDF: rasterize bitmap glyphs at 64pt, not em-size

Motivation: em-size is often results in huge bitmaps for each glyph
(e.g. 2556x2406 rgba pixels).

Define SK_PDF_BITMAP_GLYPH_RASTER_SIZE to 0 to get previous behaviour.

Define SK_PDF_BITMAP_GLYPH_RASTER_SIZE to a positive value to rasterize
at that font size rather than 64pt.

Bug: b/141094460
Bug: chromium:921585
Change-Id: I4523e512ec149cf02c985eb83f2e640a2c680d3a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/245160
Commit-Queue: Hal Canary <halcanary@skia.org>
Reviewed-by: Ben Wagner <bungeman@google.com>

src/pdf/SkPDFFont.cpp

diff --git a/src/pdf/SkPDFFont.cpp b/src/pdf/SkPDFFont.cpp
index ba79a15..c027523 100644
--- a/src/pdf/SkPDFFont.cpp
+++ b/src/pdf/SkPDFFont.cpp
@@ -511,6 +511,22 @@
     return ref;
 }
 
+#ifdef SK_PDF_BITMAP_GLYPH_RASTER_SIZE
+static constexpr float kBitmapFontSize = SK_PDF_BITMAP_GLYPH_RASTER_SIZE;
+#else
+static constexpr float kBitmapFontSize = 64;
+#endif
+
+SkStrikeSpec make_small_strike(const SkTypeface& typeface) {
+    SkFont font(sk_ref_sp(&typeface), kBitmapFontSize);
+    font.setHinting(SkFontHinting::kNone);
+    font.setEdging(SkFont::Edging::kAlias);
+    return SkStrikeSpec::MakeMask(font,
+                                  SkPaint(),
+                                  SkSurfaceProps(0, kUnknown_SkPixelGeometry),
+                                  kFakeGammaAndBoostContrast,
+                                  SkMatrix::I());
+}
 
 static void emit_subset_type3(const SkPDFFont& pdfFont, SkPDFDocument* doc) {
     SkTypeface* typeface = pdfFont.typeface();
@@ -529,6 +545,12 @@
     SkASSERT(cache);
     SkScalar emSize = (SkScalar)unitsPerEm;
 
+    SkStrikeSpec strikeSpecSmall = kBitmapFontSize > 0 ? make_small_strike(*typeface)
+                                                       : strikeSpec;
+    auto smallCache = strikeSpecSmall.findOrCreateExclusiveStrike();
+    SkASSERT(smallCache);
+    float bitmapScale = kBitmapFontSize > 0 ? emSize / kBitmapFontSize : 1.0f;
+
     SkPDFDict font("Font");
     font.insertName("Subtype", "Type3");
     // Flip about the x-axis and scale by 1/emSize.
@@ -575,20 +597,22 @@
                 SkPDFUtils::EmitPath(*path, SkPaint::kFill_Style, &content);
                 SkPDFUtils::PaintPath(SkPaint::kFill_Style, path->getFillType(), &content);
             } else {
-                auto pimg = to_image(gID, cache.get());
+                auto pimg = to_image(gID, smallCache.get());
                 if (!pimg.fImage) {
                     setGlyphWidthAndBoundingBox(glyph->advanceX(), glyphBBox, &content);
                 } else {
+                    using SkPDFUtils::AppendScalar;
                     imageGlyphs.emplace_back(gID, SkPDFSerializeImage(pimg.fImage.get(), doc));
-                    SkPDFUtils::AppendScalar(glyph->advanceX(), &content);
+                    AppendScalar(glyph->advanceX(), &content);
                     content.writeText(" 0 d0\n");
-                    content.writeDecAsText(pimg.fImage->width());
+                    AppendScalar(pimg.fImage->width() * bitmapScale, &content);
                     content.writeText(" 0 0 ");
-                    content.writeDecAsText(-pimg.fImage->height());
+                    AppendScalar(-pimg.fImage->height() * bitmapScale, &content);
                     content.writeText(" ");
-                    content.writeDecAsText(pimg.fOffset.x());
+                    AppendScalar(pimg.fOffset.x() * bitmapScale, &content);
                     content.writeText(" ");
-                    content.writeDecAsText(pimg.fImage->height() + pimg.fOffset.y());
+                    AppendScalar((pimg.fImage->height() + pimg.fOffset.y()) * bitmapScale,
+                                 &content);
                     content.writeText(" cm\n/X");
                     content.write(characterName.c_str(), characterName.size());
                     content.writeText(" Do\n");