C#图片截取压缩(百分比压缩/大小压缩)实现代码

View Code
/// <summary>
/// 按照比例缩小图片
/// </summary>
/// <param name="srcImage">要缩小的图片</param>
/// <param name="percent">缩小比例</param>
/// <returns>缩小后的结果</returns>
public static Bitmap PercentImage(Image srcImage, double percent)
{
// 缩小后的高度
int newH = int.Parse(Math.Round(srcImage.Height * percent).ToString());
// 缩小后的宽度
int newW = int.Parse(Math.Round(srcImage.Width * percent).ToString());
try
{
// 要保存到的图片
Bitmap b = new Bitmap(newW, newH);
Graphics g = Graphics.FromImage(b);
// 插值算法的质量
g.InterpolationMode = InterpolationMode.Default;
g.DrawImage(srcImage, new Rectangle(0, 0, newW, newH), new Rectangle(0, 0, srcImage.Width, srcImage.Height), GraphicsUnit.Pixel);
g.Dispose();
return b;
}
catch (Exception)
{
return null;
}
}

View Code
/// <summary>
/// 按照指定大小缩放图片
/// </summary>
/// <param name="srcImage"></param>
/// <param name="iWidth"></param>
/// <param name="iHeight"></param>
/// <returns></returns>
public static Bitmap SizeImage(Image srcImage, int iWidth, int iHeight)
{
try
{
// 要保存到的图片
Bitmap b = new Bitmap(iWidth, iHeight);
Graphics g = Graphics.FromImage(b);
// 插值算法的质量
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
g.DrawImage(srcImage, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(0, 0, srcImage.Width, srcImage.Height), GraphicsUnit.Pixel);
g.Dispose();
return b;
}
catch (Exception)
{
return null;
}
}

View Code
/// <summary>
/// 按照指定大小缩放图片，但是为了保证图片宽高比自动截取
/// </summary>
/// <param name="srcImage"></param>
/// <param name="iWidth"></param>
/// <param name="iHeight"></param>
/// <returns></returns>
public static Bitmap SizeImageWithOldPercent(Image srcImage, int iWidth, int iHeight)
{
try
{
// 要截取图片的宽度（临时图片）
int newW = srcImage.Width;
// 要截取图片的高度（临时图片）
int newH = srcImage.Height;
// 截取开始横坐标（临时图片）
int newX = 0;
// 截取开始纵坐标（临时图片）
int newY = 0;
// 截取比例（临时图片）
double whPercent = 1;
whPercent = ((double)iWidth / (double)iHeight) * ((double)srcImage.Height / (double)srcImage.Width);
if (whPercent > 1)
{
// 当前图片宽度对于要截取比例过大时
newW = int.Parse(Math.Round(srcImage.Width / whPercent).ToString());
}
else if (whPercent < 1)
{
// 当前图片高度对于要截取比例过大时
newH = int.Parse(Math.Round(srcImage.Height * whPercent).ToString());
}
if (newW != srcImage.Width)
{
// 宽度有变化时，调整开始截取的横坐标
newX = Math.Abs(int.Parse(Math.Round(((double)srcImage.Width - newW) / 2).ToString()));
}
else if (newH == srcImage.Height)
{
// 高度有变化时，调整开始截取的纵坐标
newY = Math.Abs(int.Parse(Math.Round(((double)srcImage.Height - (double)newH) / 2).ToString()));
}
// 取得符合比例的临时文件
Bitmap cutedImage = CutImage(srcImage, newX, newY, newW, newH);
// 保存到的文件
Bitmap b = new Bitmap(iWidth, iHeight);
Graphics g = Graphics.FromImage(b);
// 插值算法的质量
g.InterpolationMode = InterpolationMode.Default;
g.DrawImage(cutedImage, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(0, 0, cutedImage.Width, cutedImage.Height), GraphicsUnit.Pixel);
g.Dispose();
return b;
}
catch (Exception)
{
return null;
}
}

View Code
/// <summary>
/// jpeg图片压缩
/// </summary>
/// <param name="sFile"></param>
/// <param name="outPath"></param>
/// <param name="flag"></param>
/// <returns></returns>
public static bool GetPicThumbnail(string sFile, string outPath, int flag)
{
System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile);
ImageFormat tFormat = iSource.RawFormat;
//以下代码为保存图片时，设置压缩质量
EncoderParameters ep = new EncoderParameters();
long[] qy = new long[1];
qy[0] = flag;//设置压缩的比例1-100
EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);
ep.Param[0] = eParam;
try
{
ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
ImageCodecInfo jpegICIinfo = null;
for (int x = 0; x < arrayICI.Length; x++)
{
if (arrayICI[x].FormatDescription.Equals("JPEG"))
{
jpegICIinfo = arrayICI[x];
break;
}
}
if (jpegICIinfo != null)
{
iSource.Save(outPath, jpegICIinfo, ep);//dFile是压缩后的新路径
}
else
{
iSource.Save(outPath, tFormat);
}
return true;
}
catch
{
return false;
}
finally
{
iSource.Dispose();
iSource.Dispose();
}
}

View Code
/// <summary>
/// 剪裁 -- 用GDI+
/// </summary>
/// <param name="b">原始Bitmap</param>
/// <param name="StartX">开始坐标X</param>
/// <param name="StartY">开始坐标Y</param>
/// <param name="iWidth">宽度</param>
/// <param name="iHeight">高度</param>
/// <returns>剪裁后的Bitmap</returns>
public static Bitmap CutImage(Image b, int StartX, int StartY, int iWidth, int iHeight)
{
if (b == null)
{
return null;
}
int w = b.Width;
int h = b.Height;
if (StartX >= w || StartY >= h)
{
// 开始截取坐标过大时，结束处理
return null;
}
if (StartX + iWidth > w)
{
// 宽度过大时只截取到最大大小
iWidth = w - StartX;
}
if (StartY + iHeight > h)
{
// 高度过大时只截取到最大大小
iHeight = h - StartY;
}
try
{
Bitmap bmpOut = new Bitmap(iWidth, iHeight);
Graphics g = Graphics.FromImage(bmpOut);
g.DrawImage(b, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(StartX, StartY, iWidth, iHeight), GraphicsUnit.Pixel);
g.Dispose();
return bmpOut;
}
catch
{
return null;
}
}