我有一个包含 RGBA 编码图像的 C# 字节数组。在 WPF 中显示此图像的最佳方式是什么?
一种选择是从字节数组创建一个 BitmapSource 并将其附加到 Image 控件。但是,创建BitmapSource需要RGBA32的PixelFormat,Windows中似乎不可用。
byte[] buffer = new byte[] { 25, 166, 0, 255, 90, 0, 120, 255 };
BitmapSource.Create(2, 1, 96d, 96d, PixelFormats.Bgra32, null, buffer, 4 * 2);
我绝对不想在我的字节数组中交换像素。
最佳答案
在深入研究 WIC 的细节之前,您可以考虑将字节交换封装在一个简单的自定义 BitmapSource 中,如下所示。它需要一个 RGBA 字节数组并在重写的 CopyPixels
方法中交换像素字节以生成 PBGRA 缓冲区。
您可以通过提供 RGBA 缓冲区和位图宽度来简单地创建此自定义 BitmapSource 的实例,例如
var buffer = new byte[] { 25, 166, 0, 255, 90, 0, 120, 255 };
var bitmapSource = new RgbaBitmapSource(buffer, 2);
这是实现:
public class RgbaBitmapSource : BitmapSource
{
private byte[] rgbaBuffer;
private int pixelWidth;
private int pixelHeight;
public RgbaBitmapSource(byte[] rgbaBuffer, int pixelWidth)
{
this.rgbaBuffer = rgbaBuffer;
this.pixelWidth = pixelWidth;
this.pixelHeight = rgbaBuffer.Length / (4 * pixelWidth);
}
public override void CopyPixels(
Int32Rect sourceRect, Array pixels, int stride, int offset)
{
for (int y = sourceRect.Y; y < sourceRect.Y + sourceRect.Height; y++)
{
for (int x = sourceRect.X; x < sourceRect.X + sourceRect.Width; x++)
{
int i = stride * y + 4 * x;
byte a = rgbaBuffer[i + 3];
byte r = (byte)(rgbaBuffer[i] * a / 256); // pre-multiplied R
byte g = (byte)(rgbaBuffer[i + 1] * a / 256); // pre-multiplied G
byte b = (byte)(rgbaBuffer[i + 2] * a / 256); // pre-multiplied B
pixels.SetValue(b, i + offset);
pixels.SetValue(g, i + offset + 1);
pixels.SetValue(r, i + offset + 2);
pixels.SetValue(a, i + offset + 3);
}
}
}
protected override Freezable CreateInstanceCore()
{
return new RgbaBitmapSource(rgbaBuffer, pixelWidth);
}
public override event EventHandler<DownloadProgressEventArgs> DownloadProgress;
public override event EventHandler DownloadCompleted;
public override event EventHandler<ExceptionEventArgs> DownloadFailed;
public override event EventHandler<ExceptionEventArgs> DecodeFailed;
public override double DpiX
{
get { return 96; }
}
public override double DpiY
{
get { return 96; }
}
public override PixelFormat Format
{
get { return PixelFormats.Pbgra32; }
}
public override int PixelWidth
{
get { return pixelWidth; }
}
public override int PixelHeight
{
get { return pixelHeight; }
}
public override double Width
{
get { return pixelWidth; }
}
public override double Height
{
get { return pixelHeight; }
}
}
正如评论中所指出的,您可以通过实现不安全的复制操作来提高性能,这可能如下所示:
unsafe public override void CopyPixels(
Int32Rect sourceRect, Array pixels, int stride, int offset)
{
fixed (byte* source = rgbaBuffer, destination = (byte[])pixels)
{
byte* dstPtr = destination + offset;
for (int y = sourceRect.Y; y < sourceRect.Y + sourceRect.Height; y++)
{
for (int x = sourceRect.X; x < sourceRect.X + sourceRect.Width; x++)
{
byte* srcPtr = source + stride * y + 4 * x;
byte a = *(srcPtr + 3);
*(dstPtr++) = (byte)(*(srcPtr + 2) * a / 256); // pre-multiplied B
*(dstPtr++) = (byte)(*(srcPtr + 1) * a / 256); // pre-multiplied G
*(dstPtr++) = (byte)(*srcPtr * a / 256); // pre-multiplied R
*(dstPtr++) = a;
}
}
}
}
关于c# - 显示内存中的 RGBA 图像,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/21428272/