add SkSfntUtils to parse some known truetype tables
add comments and cleanup to count_tables in SkFontHost_tables.cpp
fix transparency bug in gifs
use (alpha+1) for blending in srcover mode, to ensure opaque results
git-svn-id: http://skia.googlecode.com/svn/trunk@155 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/utils/SkSfntUtils.cpp b/src/utils/SkSfntUtils.cpp
new file mode 100644
index 0000000..36f1f97
--- /dev/null
+++ b/src/utils/SkSfntUtils.cpp
@@ -0,0 +1,87 @@
+#include "SkEndian.h"
+#include "SkSfntUtils.h"
+
+static uint16_t parse_be16(const uint8_t*& p) {
+ uint16_t value = (p[0] << 8) | p[1];
+ p += 2;
+ return value;
+}
+
+static uint32_t parse_be32(const uint8_t*& p) {
+ uint32_t value = (p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3];
+ p += 4;
+ return value;
+}
+
+static Sk64 parse_be64(const uint8_t*& p) {
+ Sk64 value;
+ value.fHi = (p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3];
+ value.fLo = (p[4] << 24) | (p[5] << 16) | (p[6] << 8) | p[7];
+ p += 8;
+ return value;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+bool SkSfntUtils::ReadTable_head(SkFontID fontID, SkSfntTable_head* head) {
+ static const uint32_t gTag = SkSetFourByteTag('h', 'e', 'a', 'd');
+ static const ssize_t gSize = 54;
+
+ uint8_t storage[gSize];
+ ssize_t size = SkFontHost::GetTableData(fontID, gTag, 0, gSize, storage);
+ if (size != gSize) {
+ return false;
+ }
+
+ const uint8_t* p = storage;
+ head->fVersion = parse_be32(p);
+ head->fRevision = parse_be32(p);
+ head->fCheckSumAdjustment = parse_be32(p);
+ head->fMagicNumber = parse_be32(p);
+ head->fFlags = parse_be16(p);
+ head->fUnitsPerEm = parse_be16(p);
+ head->fDateCreated = parse_be64(p);
+ head->fDateModified = parse_be64(p);
+ head->fXMin = parse_be16(p);
+ head->fXMin = parse_be16(p);
+ head->fXMin = parse_be16(p);
+ head->fXMin = parse_be16(p);
+ head->fMacStyle = parse_be16(p);
+ head->fLowestPPEM = parse_be16(p);
+ head->fFontDirectionHint = parse_be16(p);
+ head->fIndexToLocFormat = parse_be16(p);
+ head->fGlyphDataFormat = parse_be16(p);
+ SkASSERT(p - storage == size);
+ return true;
+}
+
+bool SkSfntUtils::ReadTable_maxp(SkFontID fontID, SkSfntTable_maxp* maxp) {
+ static const uint32_t gTag = SkSetFourByteTag('m', 'a', 'x', 'p');
+ static const ssize_t gSize = 32;
+
+ uint8_t storage[gSize];
+ ssize_t size = SkFontHost::GetTableData(fontID, gTag, 0, gSize, storage);
+ if (size != gSize) {
+ return false;
+ }
+
+ const uint8_t* p = storage;
+ maxp->fVersion = parse_be32(p);
+ maxp->fNumGlyphs = parse_be16(p);
+ maxp->fMaxPoints = parse_be16(p);
+ maxp->fMaxContours = parse_be16(p);
+ maxp->fMaxComponentPoints = parse_be16(p);
+ maxp->fMaxComponentContours = parse_be16(p);
+ maxp->fMaxZones = parse_be16(p);
+ maxp->fMaxTwilightPoints = parse_be16(p);
+ maxp->fMaxStorage = parse_be16(p);
+ maxp->fMaxFunctionDefs = parse_be16(p);
+ maxp->fMaxInstructionDefs = parse_be16(p);
+ maxp->fMaxStackElements = parse_be16(p);
+ maxp->fMaxSizeOfInstructions = parse_be16(p);
+ maxp->fMaxComponentElements = parse_be16(p);
+ maxp->fMaxComponentDepth = parse_be16(p);
+ SkASSERT(p - storage == size);
+ return true;
+}
+