如何解决在c#中使用twain获取图像作为图像类
| 我可以使用twaindotnet连接并从设备中获取图像。但我想将图像作为“ 0”类处理。当我尝试这样的事情: ...
ArrayList pics = tw.TransferPictures();
EndingScan();
tw.CloseSrc();
if(pics.Count > 0) {
IntPtr img = (IntPtr) pics[ 0 ];
PicForm newpic = new PicForm( img );
Image r = Image.FromHbitmap(img,this.Handle);
pictureBox.Image = r;
}
...
我在行中收到\“错误:GDI +中发生一般错误”的错误,
Image r = Image.FromHbitmap(img,this.Handle);
那我在哪里错了?如何获得图像图像?
解决方法
我也发现只叫
Image.FromHbitmap
是不够的。
我在您提到的TwainDotNet库中进行了查看,然后找到了BitmapRenderer类。
仅提取相关位,就很容易使用它来创建一个简单的静态方法,您可以传入从TWAIN(在您的情况下为img变量)中获取的ѭ4并将其转换为位图。因此,您可以这样称呼它:
Image r = TwainBitmapConvertor.ToBitmap(img);
这是代码(它仅适用于x86,需要整理,但可以完成工作):
public static class TwainBitmapConvertor
{
[StructLayout(LayoutKind.Sequential,Pack = 2)]
private class BitmapInfoHeader
{
public int Size;
public int Width;
public int Height;
public short Planes;
public short BitCount;
public int Compression;
public int SizeImage;
public int XPelsPerMeter;
public int YPelsPerMeter;
public int ClrUsed;
public int ClrImportant;
}
[DllImport(\"gdi32.dll\",ExactSpelling = true)]
private static extern int SetDIBitsToDevice(IntPtr hdc,int xdst,int ydst,int width,int height,int xsrc,int ysrc,int start,int lines,IntPtr bitsptr,IntPtr bmiptr,int color);
[DllImport(\"kernel32.dll\",ExactSpelling = true)]
private static extern IntPtr GlobalLock(IntPtr handle);
[DllImport(\"kernel32.dll\",ExactSpelling = true)]
private static extern bool GlobalUnlock(IntPtr handle);
[DllImport(\"kernel32.dll\",ExactSpelling = true)]
private static extern IntPtr GlobalFree(IntPtr handle);
public static Bitmap ToBitmap(IntPtr dibHandle)
{
var bitmapPointer = GlobalLock(dibHandle);
var bitmapInfo = new BitmapInfoHeader();
Marshal.PtrToStructure(bitmapPointer,bitmapInfo);
var rectangle = new Rectangle();
rectangle.X = rectangle.Y = 0;
rectangle.Width = bitmapInfo.Width;
rectangle.Height = bitmapInfo.Height;
if (bitmapInfo.SizeImage == 0)
{
bitmapInfo.SizeImage =
((((bitmapInfo.Width * bitmapInfo.BitCount) + 31) & ~31) >> 3)
* bitmapInfo.Height;
}
// The following code only works on x86
Debug.Assert(Marshal.SizeOf(typeof(IntPtr)) == 4);
int pixelInfoPointer = bitmapInfo.ClrUsed;
if ((pixelInfoPointer == 0) && (bitmapInfo.BitCount <= 8))
{
pixelInfoPointer = 1 << bitmapInfo.BitCount;
}
pixelInfoPointer = (pixelInfoPointer * 4) + bitmapInfo.Size
+ bitmapPointer.ToInt32();
IntPtr pixelInfoIntPointer = new IntPtr(pixelInfoPointer);
Bitmap bitmap = new Bitmap(rectangle.Width,rectangle.Height);
using (Graphics graphics = Graphics.FromImage(bitmap))
{
IntPtr hdc = graphics.GetHdc();
try
{
SetDIBitsToDevice(hdc,rectangle.Width,rectangle.Height,pixelInfoIntPointer,bitmapPointer,0);
}
finally
{
graphics.ReleaseHdc(hdc);
}
}
bitmap.SetResolution(PpmToDpi(bitmapInfo.XPelsPerMeter),PpmToDpi(bitmapInfo.YPelsPerMeter));
GlobalUnlock(dibHandle);
GlobalFree(dibHandle);
return bitmap;
}
private static float PpmToDpi(double pixelsPerMeter)
{
double pixelsPerMillimeter = (double)pixelsPerMeter / 1000.0;
double dotsPerInch = pixelsPerMillimeter * 25.4;
return (float)Math.Round(dotsPerInch,2);
}
}
,假设tw.TransferPictures()
返回一个位图句柄数组,然后将Image r = ...
更改为:
Image r = Image.FromHbitmap(img);
FromHbitmap的第二个参数是GDI调色板的句柄,我怀疑您有。
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