如何在具有透明度/ alpha的画布上绘制图像

Question

那里!

我遗漏了使用等...只是简单的代码:

var image = Image.FromFile(/* my magic source */);
var bitmap = new Bitmap(image.Width, image.Height);
var canvas = Graphics.FromImage(bitmap);
var brush = new SolidBrush(/* my magic color */);
canvas.FillRectangle(brush, 0, 0, image.Width, image.Height);
canvas.DrawImage(image, new Rectangle(0, 0, image.Width, image.Height));
canvas.Save();
bitmap.Save(/* my magic target */);

我想image用alpha 55%绘制canvas.image是一个.png文件,并使用透明度本身.(注意:我不想制作image.MakeTransparent()- 它已经是透明的,我只需要一些alpha效果)

我怎么能实现这个目标？

Answer 1

试试ColorMatrix和ImageAttributes:

ColorMatrix cm = new ColorMatrix();
cm.Matrix33 = 0.55f;
ImageAttributes ia = new ImageAttributes();
ia.SetColorMatrix(cm);
canvas.DrawImage(image, new Rectangle(0, 0, image.Width, image.Height), 0, 0, image.Width, image.Height, GraphicsUnit.Pixel, ia);