图像处理

public class ImageDraw
{
public Image NewBitmap(int w, int h, float dpix, float dpiy)
{
var rt = new Bitmap(w, h);
rt.SetResolution(dpix, dpiy);
return rt;
}

/// <summary> 得到图像的指定区域.
/// </summary>
/// <param name="source"></param>
/// <param name="rect"></param>
/// <returns></returns>
public Image GetImageRect(Image source, Rectangle rect)
{
var rt = NewBitmap(rect.Width, rect.Height, source.HorizontalResolution, source.VerticalResolution);
Graphics gh = Graphics.FromImage(rt);
gh.DrawImage(source, 0, 0, rect, GraphicsUnit.Pixel);
gh.Save();
gh.Dispose();
return rt;
}

/// <summary> 拉伸图像.
/// </summary>
/// <param name="source"></param>
/// <param name="newSize"></param>
/// <returns></returns>
public Image GetStretchImage(Image source, Size newSize)
{
var w = source.Width;
var h = source.Height;

var rt = NewBitmap(newSize.Width, newSize.Height, source.HorizontalResolution, source.VerticalResolution);
var gh = Graphics.FromImage(rt);

gh.DrawImage(source, new Rectangle(0, 0, newSize.Width, newSize.Height), new Rectangle(0, 0, w, h), GraphicsUnit.Pixel);

gh.Save();
gh.Dispose();

return rt;
}

/// <summary> 拉伸图像至合适大小,并保持纵横比..
/// </summary>
/// <param name="source"></param>
/// <param name="newSize"></param>
/// <returns></returns>
public Image GetAdaptiveImage(Image source, Size newSize)
{
var sw = source.Width;
var sh = source.Height;
var tw = newSize.Width;
var th = newSize.Height;

double wb = sw * 1.0 / tw;
double hb = sh * 1.0 / th;

//计算目标图像宽高.
if (wb > hb)
{
//取宽度作为标准 
th = (int)(sh / wb);
}
else
{
tw = (int)(sw / hb);
}

//生成图像
return GetStretchImage(source, new Size(tw, th));
}

/// <summary> 剪裁图像至合适大小.
/// </summary>
/// <param name="image"></param>
/// <param name="size"></param>
/// <returns></returns>
public Image GetFillImage(Image source, Size newSize)
{
var sw = source.Width;
var sh = source.Height;
var tw = newSize.Width;
var th = newSize.Height;

double wb = sw * 1.0 / tw;
double hb = sh * 1.0 / th;

Image rt;
Graphics gh;

//计算目标图像宽高.
if (wb > hb)
{
th = sh;
tw = (int)(tw * hb);

rt = NewBitmap(newSize.Width, newSize.Height, source.HorizontalResolution, source.VerticalResolution);
gh = Graphics.FromImage(rt);

gh.DrawImage(source, new Rectangle(new Point(0, 0), newSize), new Rectangle(new Point((sw - tw) / 2, 0), new Size(tw, th)), GraphicsUnit.Pixel);
gh.Dispose();

return rt;
}
else
{
//计算出原图中要裁剪的尺寸.
tw = sw;
th = (int)(th * wb);

rt = NewBitmap(newSize.Width, newSize.Height, source.HorizontalResolution, source.VerticalResolution);
gh = Graphics.FromImage(rt);

gh.DrawImage(source, new Rectangle(0, 0, 100, 100), new Rectangle(30, 30, 100, 100), GraphicsUnit.Pixel);

gh.DrawImage(source, new Rectangle(new Point(0, 0), newSize), new Rectangle(new Point(0, (sh - th) / 2), new Size(tw, th)), GraphicsUnit.Pixel);
gh.Dispose();

return rt;
}
}

/// <summary> 获取图像数据
/// </summary>
/// <param name="img"></param>
/// <returns></returns>
public byte[] GetImageData(Image img)
{
//将图像转化为32位位图 ( 24位计算色差有些麻烦.^^ 32位,则直接转换为整数.)
var bmp = new Bitmap(img.Width, img.Height, PixelFormat.Format32bppPArgb);

bmp.SetResolution(img.HorizontalResolution, img.VerticalResolution);

var gh = Graphics.FromImage(bmp);

gh.DrawImageUnscaled(img, 0, 0);

gh.Save();

img = bmp;

gh.Dispose();

var ms = new MemoryStream(img.Width * img.Height * 4 + 2048);

img.Save(ms, ImageFormat.Bmp);
ms.Flush();
ms.Position = 0;
var data = new byte[ms.Length];
ms.Read(data, 0, data.Length);
ms.Close();
return data;
}

/// <summary> 保存图片 貌似是0 - 100
/// </summary>
/// <param name="lm"></param>
/// <param name="p"></param>
/// <param name="fn"> </param>
/// <param name="quality"> </param>
public void SaveImageToJpeg(Image lm, string fn, int quality)
{
System.IO.Directory.CreateDirectory(Path.GetDirectoryName(fn));

var sm = new FileStream(fn, FileMode.Create);
SaveImageToJpeg(lm, sm, quality);
sm.Close();
}

public void SaveImageToJpeg(Image lm, Stream stream, int quality)
{
if (quality == 0)
{
quality = 80;
}

var jgpEncoder = System.Drawing.Imaging.ImageCodecInfo.GetImageDecoders().First(j => j.FormatID == ImageFormat.Jpeg.Guid);

//参数数组
var myEncoderParameters = new System.Drawing.Imaging.EncoderParameters(1);

//质量
var myEncoder = System.Drawing.Imaging.Encoder.Quality;

//质量包含参数 
//EncoderParameters paramList = Image.FromFile("c:\\http_imgload.jpg").GetEncoderParameterList(jgpEncoder.Clsid);

var myEncoderParameter = new System.Drawing.Imaging.EncoderParameter(myEncoder, (Int64)quality);

myEncoderParameters.Param[0] = myEncoderParameter;

lm.Save(stream, jgpEncoder, myEncoderParameters);
stream.Flush();
}
}