[英]Draw Bitmap with alpha channel
I have a Format32bppArgb
backbuffer, where I draw some lines: 我有一个
Format32bppArgb
缓冲区,在其中绘制了一些线:
var g = Graphics.FromImage(bitmap);
g.Clear(Color.FromArgb(0));
var rnd = new Random();
for (int i = 0; i < 5000; i++) {
int x1 = rnd.Next(ClientRectangle.Left, ClientRectangle.Right);
int y1 = rnd.Next(ClientRectangle.Top, ClientRectangle.Bottom);
int x2 = rnd.Next(ClientRectangle.Left, ClientRectangle.Right);
int y2 = rnd.Next(ClientRectangle.Top, ClientRectangle.Bottom);
Color color = Color.FromArgb(rnd.Next(0, 255), rnd.Next(0, 255), rnd.Next(0, 255));
g.DrawLine(new Pen(color), x1, y1, x2, y2);
}
Now I want to copy bitmap
in Paint
event. 现在我想在
Paint
事件中复制bitmap
。 I do it like this: 我这样做是这样的:
void Form1Paint(object sender, PaintEventArgs e)
{
e.Graphics.DrawImageUnscaled(bitmap, 0, 0);
}
Hovewer, the DrawImageUnscaled
copies pixels and applies the alpha channel, thus pixels with alpha == 0 won't have any effect. 但是,
DrawImageUnscaled
复制像素并应用Alpha通道,因此Alpha == 0的像素将没有任何效果。 But I need raw byte copy, so pixels with alpha == 0 are also copied. 但是我需要原始字节复制,因此还复制了alpha == 0的像素。 So the result of these operations should be that
e.Graphics
contains exact byte-copy of the bitmap
. 因此,这些操作的结果应该是
e.Graphics
包含bitmap
精确字节副本。 How to do that? 怎么做?
Summary: When drawing a bitmap, I don't want to apply the alpha channel, I merely want to copy the pixels.
摘要:绘制位图时,我不想应用alpha通道,我只想复制像素。
在绘制图像之前,将Graphics.CompositingMode设置为CompositingMode.SourceCopy 。
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