C#图片按比例缩放：
// 按比例缩放图片
public Image ZoomPicture(Image SourceImage, int TargetWidth, int TargetHeight)
{
int IntWidth; //新的图片宽
int IntHeight; //新的图片高
try
{
System.Drawing.Imaging.ImageFormat format = SourceImage.RawFormat;
System.Drawing.Bitmap SaveImage = new System.Drawing.Bitmap(TargetWidth, TargetHeight);
Graphics g = Graphics.FromImage(SaveImage);
g.Clear(Color.White); //计算缩放图片的大小 http://www.cnblogs.com/roucheng/ if (SourceImage.Width > TargetWidth && SourceImage.Height <= TargetHeight)//宽度比目的图片宽度大，长度比目的图片长度小
{
IntWidth = TargetWidth;
IntHeight = (IntWidth * SourceImage.Height) / SourceImage.Width;
}
else if (SourceImage.Width <= TargetWidth && SourceImage.Height > TargetHeight)//宽度比目的图片宽度小，长度比目的图片长度大
{
IntHeight = TargetHeight;
IntWidth = (IntHeight * SourceImage.Width) / SourceImage.Height;
}
else if (SourceImage.Width <= TargetWidth && SourceImage.Height <= TargetHeight) //长宽比目的图片长宽都小
{
IntHeight = SourceImage.Width;
IntWidth = SourceImage.Height;
}
else//长宽比目的图片的长宽都大
{
IntWidth = TargetWidth;
IntHeight = (IntWidth * SourceImage.Height) / SourceImage.Width;
if (IntHeight > TargetHeight)//重新计算
{
IntHeight = TargetHeight;
IntWidth = (IntHeight * SourceImage.Width) / SourceImage.Height;
}
} g.DrawImage(SourceImage, (TargetWidth - IntWidth) / , (TargetHeight - IntHeight) / , IntWidth, IntHeight);
SourceImage.Dispose(); return SaveImage;
}
catch (Exception ex)
{ } return null;
}