Net compact Framework居然不支持透明 PNG
才发现 .Net compact Framework居然不支持透明 PNG.太弱了。 In case someone run into same problem, there's one solution for this problem.it uses IImagingFactory etc to solve this problem.
在Windows Mobile 显示透明 PNG的方法
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。http://hi.csdn.net/attachment/201010/13/0_12869534069cr3.gif
两个图片叠加形成最后的图片
http://hi.csdn.net/attachment/201010/13/0_1286953618J8RR.gif
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
using System;
using System.Drawing;
using System.Runtime.InteropServices;
namespace DotNetPocketStreet.Drawing
{
enum ImageLockMode
{
ImageLockModeRead = 0x0001,
ImageLockModeWrite = 0x0002,
ImageLockModeUserInputBuf = 0x0004
};
// Pulled from gdipluspixelformats.h in the Windows Mobile 5.0 Pocket PC SDK
public enum PixelFormatID : int
{
PixelFormatIndexed = 0x00010000, // Indexes into a palette
PixelFormatGDI = 0x00020000, // Is a GDI-supported format
PixelFormatAlpha = 0x00040000, // Has an alpha component
PixelFormatPAlpha = 0x00080000, // Pre-multiplied alpha
PixelFormatExtended = 0x00100000, // Extended color 16 bits/channel
PixelFormatCanonical = 0x00200000,
PixelFormatUndefined = 0,
PixelFormatDontCare = 0,
PixelFormat1bppIndexed = (1 | ( 1 << 8) | PixelFormatIndexed | PixelFormatGDI),
PixelFormat4bppIndexed = (2 | ( 4 << 8) | PixelFormatIndexed | PixelFormatGDI),
PixelFormat8bppIndexed = (3 | ( 8 << 8) | PixelFormatIndexed | PixelFormatGDI),
PixelFormat16bppRGB555 = (5 | (16 << 8) | PixelFormatGDI),
PixelFormat16bppRGB565 = (6 | (16 << 8) | PixelFormatGDI),
PixelFormat16bppARGB1555 = (7 | (16 << 8) | PixelFormatAlpha | PixelFormatGDI),
PixelFormat24bppRGB = (8 | (24 << 8) | PixelFormatGDI),
PixelFormat32bppRGB = (9 | (32 << 8) | PixelFormatGDI),
PixelFormat32bppARGB = (10 | (32 << 8) | PixelFormatAlpha | PixelFormatGDI | PixelFormatCanonical),
PixelFormat32bppPARGB = (11 | (32 << 8) | PixelFormatAlpha | PixelFormatPAlpha | PixelFormatGDI),
PixelFormat48bppRGB = (12 | (48 << 8) | PixelFormatExtended),
PixelFormat64bppARGB = (13 | (64 << 8) | PixelFormatAlpha | PixelFormatCanonical | PixelFormatExtended),
PixelFormat64bppPARGB = (14 | (64 << 8) | PixelFormatAlpha | PixelFormatPAlpha | PixelFormatExtended),
PixelFormatMax = 15
}
// Pulled from imaging.h in the Windows Mobile 5.0 Pocket PC SDK
public enum BufferDisposalFlag : int
{
BufferDisposalFlagNone,
BufferDisposalFlagGlobalFree,
BufferDisposalFlagCoTaskMemFree,
BufferDisposalFlagUnmapView
}
// Pulled from imaging.h in the Windows Mobile 5.0 Pocket PC SDK
public enum InterpolationHint : int
{
InterpolationHintDefault,
InterpolationHintNearestNeighbor,
InterpolationHintBilinear,
InterpolationHintAveraging,
InterpolationHintBicubic
}
// Pulled from gdiplusimaging.h in the Windows Mobile 5.0 Pocket PC SDK
public struct BitmapData
{
public uint Width;
public uint Height;
public int Stride;
public PixelFormatID PixelFormat;
public IntPtr Scan0;
public IntPtr Reserved;
}
// Pulled from imaging.h in the Windows Mobile 5.0 Pocket PC SDK
public struct ImageInfo
{
public uint GuidPart1; // I am being lazy here, I don't care at this point about the RawDataFormat GUID
public uint GuidPart2; // I am being lazy here, I don't care at this point about the RawDataFormat GUID
public uint GuidPart3; // I am being lazy here, I don't care at this point about the RawDataFormat GUID
public uint GuidPart4; // I am being lazy here, I don't care at this point about the RawDataFormat GUID
public PixelFormatID pixelFormat;
public uint Width;
public uint Height;
public uint TileWidth;
public uint TileHeight;
public double Xdpi;
public double Ydpi;
public uint Flags;
}
// Pulled from imaging.h in the Windows Mobile 5.0 Pocket PC SDK
public interface IImagingFactory
{
uint CreateImageFromStream(); // This is a place holder, note the lack of arguments
uint CreateImageFromFile(string filename, out INativeImage image);
// We need the MarshalAs attribute here to keep COM interop from sending the buffer down as a Safe Array.
uint CreateImageFromBuffer( byte[] buffer, uint size, BufferDisposalFlag disposalFlag, out INativeImage image);
uint CreateNewBitmap(uint width, uint height, PixelFormatID pixelFormat, out IBitmapImage bitmap);
uint CreateBitmapFromImage(INativeImage image, uint width, uint height, PixelFormatID pixelFormat, InterpolationHint hints, out IBitmapImage bitmap);
uint CreateBitmapFromBuffer(); // This is a place holder, note the lack of arguments
uint CreateImageDecoder(); // This is a place holder, note the lack of arguments
uint CreateImageEncoderToStream(); // This is a place holder, note the lack of arguments
uint CreateImageEncoderToFile(); // This is a place holder, note the lack of arguments
uint GetInstalledDecoders(); // This is a place holder, note the lack of arguments
uint GetInstalledEncoders(); // This is a place holder, note the lack of arguments
uint InstallImageCodec(); // This is a place holder, note the lack of arguments
uint UninstallImageCodec(); // This is a place holder, note the lack of arguments
}
// Pulled from imaging.h in the Windows Mobile 5.0 Pocket PC SDK
public interface INativeImage
{
uint GetPhysicalDimension(out Size size);
uint GetImageInfo(out ImageInfo info);
uint SetImageFlags(uint flags);
uint Draw(IntPtr hdc, ref Rectangle dstRect, IntPtr NULL); // "Correct" declaration: uint Draw(IntPtr hdc, ref Rectangle dstRect, ref Rectangle srcRect);
uint PushIntoSink(); // This is a place holder, note the lack of arguments
uint GetThumbnail(uint thumbWidth, uint thumbHeight, out INativeImage thumbImage);
}
// Pulled from imaging.h in the Windows Mobile 5.0 Pocket PC SDK
public interface IBitmapImage
{
uint GetSize(out Size size);
uint GetPixelFormatID(out PixelFormatID pixelFormat);
uint LockBits(ref Rectangle rect, uint flags, PixelFormatID pixelFormat, out BitmapData lockedBitmapData);
uint UnlockBits(ref BitmapData lockedBitmapData);
uint GetPalette(); // This is a place holder, note the lack of arguments
uint SetPalette(); // This is a place holder, note the lack of arguments
}
}
调用方法如下
using (Graphics gxBuffer = Graphics.FromImage(backBuffer))
{
// Since we nop'd OnPaintBackground, take care of it here
gxBuffer.Clear(this.BackColor);
// Ask the Image object from Imaging to draw itself.
IntPtr hdcDest = gxBuffer.GetHdc();
Rectangle dstRect = new Rectangle(100, 100, 148, 148);
imagingResource.Draw(hdcDest, ref dstRect, IntPtr.Zero);
gxBuffer.ReleaseHdc(hdcDest);
// Ask the Image object from Imaging to draw itself.
/*IntPtr*/ hdcDest = gxBuffer.GetHdc(); // This is redundant, but keeps the necessary code together
/*Rectangle*/ dstRect = new Rectangle(50, 70, 50+132, 70+132);
imagingImage.Draw(hdcDest, ref dstRect, IntPtr.Zero);
gxBuffer.ReleaseHdc(hdcDest);
}
// Put the final composed image on screen.
e.Graphics.DrawImage(backBuffer, 0, 0);
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
ImageAttributes _imageAttributes = new ImageAttributes();
Color color = Color.FromArgb(0xE0E0E0);
_imageAttributes.SetColorKey(color, color);
Rectangle dstRect = new Rectangle(x, y, netImage.GetWidth(), netImage.GetHeight());
gxBuffer.DrawImage(netImage._bitmap, dstRect, 0, 0, netImage.GetWidth(),
netImage.GetHeight(),
GraphicsUnit.Pixel, _imageAttributes);
最终结果如下图：
http://hi.csdn.net/attachment/201010/13/0_12869544289oIV.gif
[ 本帖最后由 trisun 于 13-10-2010 18:43 编辑 ]
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