前言
一、WriteableBitmap是什么？
二、如何实现
1.创建WriteableBitmap
2.写入数据
三、完整代码
四、使用示例
1.直接转换
2.复用写入
总结
前言在wpf中我们有时候需要截屏或者获取鼠标标时通常拿到的是Bitmap，如果要作显示，则需要将Bitmap转成wpf控件兼容的图像对象，比如转成BitmapSource在网上已经可以查到实现方法，这里提供一种将Bitmap转成WriteableBitmap的方法。
一、WriteableBitmap是什么？WriteableBitmap是一个wpf对象，在命名空间System.Windows.Media.Imaging中，是BitmapSource的子类。如下图所示：
创建一个与Bitmap大小相同，像素格式兼容的WriteableBitmap。
示例如下：
WriteableBitmap wb = new WriteableBitmap(bitmap.Width, bitmap.Height, 0, 0, System.Windows.Media.PixelFormats.Bgra32, null);
2.写入数据
调用Bitmap的LockBits获取其内部的图像数据，通过WritePixels的方式写入WriteableBitmap，这样即完成了转换。
示例如下：
var data = bitmap.LockBits(new System.Drawing.Rectangle(new System.Drawing.Point(0, 0), bitmap.Size), System.Drawing.Imaging.ImageLockMode.ReadOnly, src.PixelFormat);
wb.WritePixels(new Int32Rect(srcRect.X, srcRect.Y, srcRect.Width, srcRect.Height), data.Scan0, data.Height * data.Stride, data.Stride, destinationX, destinationY);
bitmap.UnlockBits(data);
三、完整代码
//将Bitmap 转换成WriteableBitmap
public static WriteableBitmap BitmapToWriteableBitmap(System.Drawing.Bitmap src)
{
var wb = CreateCompatibleWriteableBitmap(src);
System.Drawing.Imaging.PixelFormat format = src.PixelFormat;
if (wb == null)
{
wb = new WriteableBitmap(src.Width, src.Height, 0, 0, System.Windows.Media.PixelFormats.Bgra32, null);
format = System.Drawing.Imaging.PixelFormat.Format32bppArgb;
}
BitmapCopyToWriteableBitmap(src, wb, new System.Drawing.Rectangle(0, 0, src.Width, src.Height), 0, 0, format);
return wb;
}
//创建尺寸和格式与Bitmap兼容的WriteableBitmap
public static WriteableBitmap CreateCompatibleWriteableBitmap(System.Drawing.Bitmap src)
{
System.Windows.Media.PixelFormat format;
switch (src.PixelFormat)
{
case System.Drawing.Imaging.PixelFormat.Format16bppRgb555:
format = System.Windows.Media.PixelFormats.Bgr555;
break;
case System.Drawing.Imaging.PixelFormat.Format16bppRgb565:
format = System.Windows.Media.PixelFormats.Bgr565;
break;
case System.Drawing.Imaging.PixelFormat.Format24bppRgb:
format = System.Windows.Media.PixelFormats.Bgr24;
break;
case System.Drawing.Imaging.PixelFormat.Format32bppRgb:
format = System.Windows.Media.PixelFormats.Bgr32;
break;
case System.Drawing.Imaging.PixelFormat.Format32bppPArgb:
format = System.Windows.Media.PixelFormats.Pbgra32;
break;
case System.Drawing.Imaging.PixelFormat.Format32bppArgb:
format = System.Windows.Media.PixelFormats.Bgra32;
break;
default:
return null;
}
return new WriteableBitmap(src.Width, src.Height, 0, 0, format, null);
}
//将Bitmap数据写入WriteableBitmap中
public static void BitmapCopyToWriteableBitmap(System.Drawing.Bitmap src, WriteableBitmap dst, System.Drawing.Rectangle srcRect, int destinationX, int destinationY, System.Drawing.Imaging.PixelFormat srcPixelFormat)
{
var data = src.LockBits(new System.Drawing.Rectangle(new System.Drawing.Point(0, 0), src.Size), System.Drawing.Imaging.ImageLockMode.ReadOnly, srcPixelFormat);
dst.WritePixels(new Int32Rect(srcRect.X, srcRect.Y, srcRect.Width, srcRect.Height), data.Scan0, data.Height * data.Stride, data.Stride, destinationX, destinationY);
src.UnlockBits(data);
}
四、使用示例
1.直接转换
//创建一个Bitmap对象
var bitmap = new System.Drawing.Bitmap(width, height, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
//绘制Bitmap
//略
//绘制Bitmap--end
//将Bitmap转换为WriteableBitmap
var wb=BitmapToWriteableBitmap(bitmap);
2.复用写入
//创建一个Bitmap对象
var bitmap = new System.Drawing.Bitmap(width, height, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
//创建格式兼容的WriteableBitmap
var wb = CreateCompatibleWriteableBitmap(bitmap);
System.Drawing.Imaging.PixelFormat format = bitmap .PixelFormat;
if (wb == null)
//格式不兼容则强制使用bgr32
{
wb = new WriteableBitmap(bitmap .Width, bitmap .Height, 0, 0, System.Windows.Media.PixelFormats.Bgra32, null);
format = System.Drawing.Imaging.PixelFormat.Format32bppArgb;
}
while (true)
{
//绘制Bitmap
//略
//绘制Bitmap--end
//将Bitmap数据写入WriteableBitmap
BitmapCopyToWriteableBitmap(bitmap, wb, new System.Drawing.Rectangle(0, 0, bitmap.Width, bitmap.Height), 0, 0, format);
}
总结
以上就是今天要讲的内容，本质上就是对图像数据的直接拷贝，刚好Bitmap有获取内部数据的接口，而WriteableBitmap也刚好有写入数据的接口。这种方法避免了新的句柄产生，不会出现内存泄漏。而且直接的数据拷贝，不需要编解码，性能是非常好的。
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