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#6 account for hintmask and cntrmask data when parsing a type 2 charstring

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Eliot Jones
2018-11-17 19:06:21 +00:00
parent 936e17b723
commit aa6f55c9ad
1 changed files with 51 additions and 2 deletions
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53
src/UglyToad.PdfPig/Fonts/CompactFontFormat/CharStrings/Type2CharStringParser.cs
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@@ -17,6 +17,14 @@
/// </remarks>
internal class Type2CharStringParser
{
private static readonly HashSet<string> HintingCommandNames = new HashSet<string>
{
"hstem",
"vstem",
"hstemhm",
"vstemhm"
};
private static readonly IReadOnlyDictionary<int, LazyType2Command> SingleByteCommandStore = new Dictionary<int, LazyType2Command>
{
{ 1, new LazyType2Command("hstem", ctx =>
@@ -701,7 +709,7 @@
var b = bytes[i];
if (b <= 31 && b != 28)
{
var command = GetCommand(b, bytes, ref i);
var command = GetCommand(b, bytes, instructions, ref i);
instructions.Add(Union<decimal, LazyType2Command>.Two(command));
}
else
@@ -754,7 +762,8 @@
return lead + (fractionalPart / 65535m);
}
private static LazyType2Command GetCommand(byte b, IReadOnlyList<byte> bytes, ref int i)
private static LazyType2Command GetCommand(byte b, IReadOnlyList<byte> bytes,
IReadOnlyList<Union<decimal, LazyType2Command>> precedingCommands, ref int i)
{
if (b == 12)
{
@@ -767,6 +776,46 @@
return new LazyType2Command($"unknown: {b} {b2}", x => { });
}
// hintmask and cntrmask
if (b == 19 || b == 20)
{
/*
* The hintmask operator is followed by one or more data bytes that specify the stem hints which are to be active for the
* subsequent path construction. The number of data bytes must be exactly the number needed to represent the number of
* stems in the original stem list (those stems specified by the hstem, vstem, hstemhm, or vstemhm commands), using one bit
* in the data bytes for each stem in the original stem list.
*/
var stemCount = 0;
var precedingNumbers = 0;
for (var j = 0; j < precedingCommands.Count; j++)
{
var item = precedingCommands[j];
item.Match(x => precedingNumbers++,
x =>
{
if (!HintingCommandNames.Contains(x.Name))
{
precedingNumbers = 0;
return;
}
// ReSharper disable once AccessToModifiedClosure
stemCount += precedingNumbers / 2;
precedingNumbers = 0;
});
}
// The vstem command can be left out, e.g. for 12 20 hstemhm 4 6 hintmask, 4 and 6 act as the vertical hints
if (precedingNumbers > 0)
{
stemCount += precedingNumbers / 2;
}
var minimumFullBytes = Math.Ceiling(stemCount / 8d);
// Skip the following hintmask or cntrmask data bytes
i += (int)minimumFullBytes;
}
if (SingleByteCommandStore.TryGetValue(b, out var command))
{
return command;