逐个像素进行Alpha值的设置,网上其他的代码不能处理有透明背景的图片,因此要对Alpha、R、G、B均为0的透明色进行特殊处理,不做转换。
cs
private Bitmap SetImageOpacity(Image srcImage, int opacity)
{
Bitmap pic = new Bitmap(srcImage);
for (int w = 0; w < pic.Width; w++)
{
for (int h = 0; h < pic.Height; h++)
{
Color c = pic.GetPixel(w, h);
Color newC;
if (!c.Equals(Color.FromArgb(0, 0, 0, 0)))
{
newC = Color.FromArgb(opacity, c);
}
else
{
newC = c;
}
pic.SetPixel(w, h, newC);
}
}
return pic;
}
private Image SetImageOpacity2(Image srcImage, int opacity)
{
Bitmap img = new Bitmap(srcImage);
using (Bitmap bmp = new Bitmap(img.Width, img.Height, System.Drawing.Imaging.PixelFormat.Format32bppArgb))
{
using (Graphics g = Graphics.FromImage(bmp))
{
g.DrawImage(img, 0, 0);
for (int h = 0; h <= img.Height - 1; h++)
{
for (int w = 0; w <= img.Width - 1; w++)
{
Color c = img.GetPixel(w, h);
if (!c.Equals(Color.FromArgb(0, 0, 0, 0)))
{
bmp.SetPixel(w, h, Color.FromArgb(opacity, c.R, c.G, c.B));
}
else
{
bmp.SetPixel(w, h, Color.FromArgb(c.A, c.R, c.G, c.B));
}
}
}
}
return (Image)bmp.Clone();
}
}