c# - 如何将旧式 Windows 图元文件写入文件

Question

我可以生成一个旧的(未增强的)图元文件。我怎样才能将它写入磁盘以使其成为正确的 .wmf 文件？

Answer 1

Petzold doesn't mention it , 但有一个将图元文件写入磁盘的约定:在图元文件数据前加上 WmfPlaceableFileHeader structure 前缀.显然这是 invented by Aldus, back int the day并称为“可放置图元文件”。

[StructLayout(LayoutKind.Sequential, Pack = 1)]
public struct WmfPlaceableFileHeader
{
     public uint key;  // 0x9aC6CDD7
     public ushort hmf;
     public ushort bboxLeft;
     public ushort bboxTop;
     public ushort bboxRight;
     public ushort bboxBottom;
     public ushort inch;
     public uint reserved;
     public ushort checksum;
}

Win32.WmfPlaceableFileHeader header = new Win32.WmfPlaceableFileHeader();
const ushorttwips_per_inch = 1440;
header.key = 0x9aC6CDD7;  // magic number
header.hmf = 0;
header.bboxLeft = 0;
header.bboxRight = width_in_inches * twips_per_inch;
header.bboxTop = 0;
header.bboxBottom = height_in_inches * twips_per_inch;
header.inch = twips_per_inch;
header.reserved = 0;

// Calculate checksum for first 10 WORDs.
ushort checksum = 0;
byte[] header_bytes = StructureToByteArray(header);
for (int i = 0; i < 10; i++)
     checksum ^= BitConverter.ToUInt16(header_bytes, i * 2);
header.checksum = checksum;

// Construct the file in-memory.
header_bytes = StructureToByteArray(header);
file_contents.Write(header_bytes, 0, header_bytes.Length);
file_contents.Write(metafile_bytes, 0, metafile_bytes.Length);