Question

C#中图片白色转为透明，如何保存为PNG格式？

if (pictureBox1.Image == null)
return;
Bitmap bmp = new Bitmap(pictureBox1.Image, pictureBox1.Image.Size);
BitmapData data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadWrite, bmp.PixelFormat);
int length = data.Stride * data.Height;
IntPtr ptr = data.Scan0;
byte[] buff = new byte[length];
Marshal.Copy(ptr, buff, 0, length);
for (int i = 3; i < length; i += 4)
{
if (buff[i - 1] >= 230 && buff[i - 2] >= 230 && buff[i - 3] >= 230)
{
buff[i] = 0;
}
}
Marshal.Copy(buff, 0, ptr, length);
bmp.UnlockBits(data);

pictureBox2.Image = bmp;

我改成上面的代码，实现了透明功能，但是，怎么讲pictureBox2.Image 保存为PNG图片？？？

Answer 1

bmp.Save(System.Web.HttpContext.Current.Server.MapPath("文件名"), ImageFormat.Png);

追问

如果要存到内存TEMP中呢？改怎么做？

追答

bmp.Save(Path.GetTempPath()+文件名, ImageFormat.Png);