Net compact Framework居然不支持透明 PNG

trisun

才发现 .Net compact Framework居然不支持透明 PNG.太弱了。

trisun

In case someone run into same problem, there's one solution for this problem.

it uses IImagingFactory etc to solve this problem.

trisun

同样在移植的过程中，发现 .Net compact Framework 不支持透明图像。原本具有透明属性的Png (含有 alpha通道），通过 Graphics.DrawImage 显示之后，不再具有透明特性。这对于地图分层显示带了麻烦。举例来说。带地名卫星地图一般是由两层图片叠加而成。

                               
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两个图片叠加形成最后的图片

                               
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当由于.Net Compact Framework缺省不支持透明图像，两幅图叠加是 道路图回彻底覆盖掉下面的卫星图。原来的透明色变成白色。 同样如果再有其它图层（比如路径），又覆盖掉道路图。

经过Google 搜索，有两种方法可以实现在Windows mobile 上透明图像的显示。

一是通过IImagingFactory 接口

1. 
   
2. 
   
3. using System;
   
4. using System.Drawing;
   
5. using System.Runtime.InteropServices;
   
6. namespace DotNetPocketStreet.Drawing
   
7. {
   
8. enum ImageLockMode
   
9. {
   
10. ImageLockModeRead = 0x0001,
    
11. ImageLockModeWrite = 0x0002,
    
12. ImageLockModeUserInputBuf = 0x0004
    
13. };
    
14. // Pulled from gdipluspixelformats.h in the Windows Mobile 5.0 Pocket PC SDK
    
15. public enum PixelFormatID : int
    
16. {
    
17. PixelFormatIndexed = 0x00010000, // Indexes into a palette
    
18. PixelFormatGDI = 0x00020000, // Is a GDI-supported format
    
19. PixelFormatAlpha = 0x00040000, // Has an alpha component
    
20. PixelFormatPAlpha = 0x00080000, // Pre-multiplied alpha
    
21. PixelFormatExtended = 0x00100000, // Extended color 16 bits/channel
    
22. PixelFormatCanonical = 0x00200000,
    
23. PixelFormatUndefined = 0,
    
24. PixelFormatDontCare = 0,
    
25. PixelFormat1bppIndexed = (1 | ( 1 << 8) | PixelFormatIndexed | PixelFormatGDI),
    
26. PixelFormat4bppIndexed = (2 | ( 4 << 8) | PixelFormatIndexed | PixelFormatGDI),
    
27. PixelFormat8bppIndexed = (3 | ( 8 << 8) | PixelFormatIndexed | PixelFormatGDI),
    
28. PixelFormat16bppRGB555 = (5 | (16 << 8) | PixelFormatGDI),
    
29. PixelFormat16bppRGB565 = (6 | (16 << 8) | PixelFormatGDI),
    
30. PixelFormat16bppARGB1555 = (7 | (16 << 8) | PixelFormatAlpha | PixelFormatGDI),
    
31. PixelFormat24bppRGB = (8 | (24 << 8) | PixelFormatGDI),
    
32. PixelFormat32bppRGB = (9 | (32 << 8) | PixelFormatGDI),
    
33. PixelFormat32bppARGB = (10 | (32 << 8) | PixelFormatAlpha | PixelFormatGDI | PixelFormatCanonical),
    
34. PixelFormat32bppPARGB = (11 | (32 << 8) | PixelFormatAlpha | PixelFormatPAlpha | PixelFormatGDI),
    
35. PixelFormat48bppRGB = (12 | (48 << 8) | PixelFormatExtended),
    
36. PixelFormat64bppARGB = (13 | (64 << 8) | PixelFormatAlpha | PixelFormatCanonical | PixelFormatExtended),
    
37. PixelFormat64bppPARGB = (14 | (64 << 8) | PixelFormatAlpha | PixelFormatPAlpha | PixelFormatExtended),
    
38. PixelFormatMax = 15
    
39. }
    
40. // Pulled from imaging.h in the Windows Mobile 5.0 Pocket PC SDK
    
41. public enum BufferDisposalFlag : int
    
42. {
    
43. BufferDisposalFlagNone,
    
44. BufferDisposalFlagGlobalFree,
    
45. BufferDisposalFlagCoTaskMemFree,
    
46. BufferDisposalFlagUnmapView
    
47. }
    
48. // Pulled from imaging.h in the Windows Mobile 5.0 Pocket PC SDK
    
49. public enum InterpolationHint : int
    
50. {
    
51. InterpolationHintDefault,
    
52. InterpolationHintNearestNeighbor,
    
53. InterpolationHintBilinear,
    
54. InterpolationHintAveraging,
    
55. InterpolationHintBicubic
    
56. }
    
57. // Pulled from gdiplusimaging.h in the Windows Mobile 5.0 Pocket PC SDK
    
58. public struct BitmapData
    
59. {
    
60. public uint Width;
    
61. public uint Height;
    
62. public int Stride;
    
63. public PixelFormatID PixelFormat;
    
64. public IntPtr Scan0;
    
65. public IntPtr Reserved;
    
66. }
    
67. // Pulled from imaging.h in the Windows Mobile 5.0 Pocket PC SDK
    
68. public struct ImageInfo
    
69. {
    
70. public uint GuidPart1; // I am being lazy here, I don't care at this point about the RawDataFormat GUID
    
71. public uint GuidPart2; // I am being lazy here, I don't care at this point about the RawDataFormat GUID
    
72. public uint GuidPart3; // I am being lazy here, I don't care at this point about the RawDataFormat GUID
    
73. public uint GuidPart4; // I am being lazy here, I don't care at this point about the RawDataFormat GUID
    
74. public PixelFormatID pixelFormat;
    
75. public uint Width;
    
76. public uint Height;
    
77. public uint TileWidth;
    
78. public uint TileHeight;
    
79. public double Xdpi;
    
80. public double Ydpi;
    
81. public uint Flags;
    
82. }
    
83. // Pulled from imaging.h in the Windows Mobile 5.0 Pocket PC SDK
    
84. [ComImport, Guid("327ABDA7-072B-11D3-9D7B-0000F81EF32E"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    
85. [ComVisible(true)]
    
86. public interface IImagingFactory
    
87. {
    
88. uint CreateImageFromStream(); // This is a place holder, note the lack of arguments
    
89. uint CreateImageFromFile(string filename, out INativeImage image);
    
90. // We need the MarshalAs attribute here to keep COM interop from sending the buffer down as a Safe Array.
    
91. uint CreateImageFromBuffer([MarshalAs(UnmanagedType.LPArray)] byte[] buffer, uint size, BufferDisposalFlag disposalFlag, out INativeImage image);
    
92. uint CreateNewBitmap(uint width, uint height, PixelFormatID pixelFormat, out IBitmapImage bitmap);
    
93. uint CreateBitmapFromImage(INativeImage image, uint width, uint height, PixelFormatID pixelFormat, InterpolationHint hints, out IBitmapImage bitmap);
    
94. uint CreateBitmapFromBuffer(); // This is a place holder, note the lack of arguments
    
95. uint CreateImageDecoder(); // This is a place holder, note the lack of arguments
    
96. uint CreateImageEncoderToStream(); // This is a place holder, note the lack of arguments
    
97. uint CreateImageEncoderToFile(); // This is a place holder, note the lack of arguments
    
98. uint GetInstalledDecoders(); // This is a place holder, note the lack of arguments
    
99. uint GetInstalledEncoders(); // This is a place holder, note the lack of arguments
    
100. uint InstallImageCodec(); // This is a place holder, note the lack of arguments
     
101. uint UninstallImageCodec(); // This is a place holder, note the lack of arguments
     
102. }
     
103. // Pulled from imaging.h in the Windows Mobile 5.0 Pocket PC SDK
     
104. [ComImport, Guid("327ABDA9-072B-11D3-9D7B-0000F81EF32E"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
     
105. [ComVisible(true)]
     
106. public interface INativeImage
     
107. {
     
108. uint GetPhysicalDimension(out Size size);
     
109. uint GetImageInfo(out ImageInfo info);
     
110. uint SetImageFlags(uint flags);
     
111. uint Draw(IntPtr hdc, ref Rectangle dstRect, IntPtr NULL); // "Correct" declaration: uint Draw(IntPtr hdc, ref Rectangle dstRect, ref Rectangle srcRect);
     
112. uint PushIntoSink(); // This is a place holder, note the lack of arguments
     
113. uint GetThumbnail(uint thumbWidth, uint thumbHeight, out INativeImage thumbImage);
     
114. }
     
115. // Pulled from imaging.h in the Windows Mobile 5.0 Pocket PC SDK
     
116. [ComImport, Guid("327ABDAA-072B-11D3-9D7B-0000F81EF32E"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
     
117. [ComVisible(true)]
     
118. public interface IBitmapImage
     
119. {
     
120. uint GetSize(out Size size);
     
121. uint GetPixelFormatID(out PixelFormatID pixelFormat);
     
122. uint LockBits(ref Rectangle rect, uint flags, PixelFormatID pixelFormat, out BitmapData lockedBitmapData);
     
123. uint UnlockBits(ref BitmapData lockedBitmapData);
     
124. uint GetPalette(); // This is a place holder, note the lack of arguments
     
125. uint SetPalette(); // This is a place holder, note the lack of arguments
     
126. }
     
127. }

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调用方法如下

1. 
   
2. 
   
3.           using (Graphics gxBuffer = Graphics.FromImage(backBuffer))
   
4.                 {
   
5.                     // Since we nop'd OnPaintBackground, take care of it here
   
6.                     gxBuffer.Clear(this.BackColor);
   
7.                     // Ask the Image object from Imaging to draw itself.
   
8.                     IntPtr hdcDest = gxBuffer.GetHdc();
   
9.                     Rectangle dstRect = new Rectangle(100, 100, 148, 148);
   
10.                     imagingResource.Draw(hdcDest, ref dstRect, IntPtr.Zero);
    
11.                     gxBuffer.ReleaseHdc(hdcDest);
    
12.                     // Ask the Image object from Imaging to draw itself.
    
13.                     /*IntPtr*/ hdcDest = gxBuffer.GetHdc(); // This is redundant, but keeps the necessary code together
    
14.                     /*Rectangle*/ dstRect = new Rectangle(50, 70, 50+132, 70+132);
    
15.                     imagingImage.Draw(hdcDest, ref dstRect, IntPtr.Zero);
    
16.                     gxBuffer.ReleaseHdc(hdcDest);
    
17.                 }
    
18.                 // Put the final composed image on screen.
    
19.                 e.Graphics.DrawImage(backBuffer, 0, 0);

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文档可参考 http://msdn.microsoft.com/en-us/library/aa452202.aspx

另外一种方法还是采用Manged code, 对于预先知道透明色值的图像，比如地图API中的路径，背景色总为0xFFE0E0E0

可以使用下面方法

1. 
   
2. ImageAttributes _imageAttributes = new ImageAttributes();
   
3. Color color = Color.FromArgb(0xE0E0E0);
   
4. _imageAttributes.SetColorKey(color, color);
   
5. Rectangle dstRect = new Rectangle(x, y, netImage.GetWidth(), netImage.GetHeight());
   
6. gxBuffer.DrawImage(netImage._bitmap, dstRect, 0, 0, netImage.GetWidth(),
   
7.                                                    netImage.GetHeight(),
   
8.                                                    GraphicsUnit.Pixel, _imageAttributes);

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最终结果如下图：

                               
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[ 本帖最后由 trisun 于 13-10-2010 18:43 编辑 ]