C#中对图片的操作主要是通过System.Drawing.Image等类进行。
一、将图片转换为字节流
/// <summary>
/// 图片处理帮助类
/// </summary>
public static class PicProcessHelper
{
/// <summary>
/// 将图片转换为指定的字节流
/// </summary>
/// <param name="filePath">图片路径</param>
/// <returns>指定的字节流</returns>
public static byte[] ConvertToByte(String filePath)
{
var m = new System.IO.MemoryStream();
var bp = new System.Drawing.Bitmap(filePath);
bp.Save(m, System.Drawing.Imaging.ImageFormat.Jpeg); //将此图像以指定的格式保存到指定的流中。
byte[] imgByte = m.GetBuffer(); //从内存缓冲区中读取
return imgByte;
}
}
二、将字节流转换回图片
/// <summary>
/// 根据字节流返回Image类型
/// </summary>
/// <param name="streamByte"></param>
/// <returns></returns>
public static Image ReturnImage(byte[] streamByte)
{
System.IO.MemoryStream ms = new System.IO.MemoryStream(streamByte);
Image img = Image.FromStream(ms);
return img;
}
三、将Image对象转换为字节流
//将Image转换成流数据，并保存为byte[]
public static byte[] PhotoImageInsert(System.Drawing.Image imgPhoto)
{
MemoryStream mstream = new MemoryStream();
imgPhoto.Save(mstream, System.Drawing.Imaging.ImageFormat.Bmp);
byte[] byData = new Byte[mstream.Length];
mstream.Position = ;
mstream.Read(byData, , byData.Length); mstream.Close();
return byData;
}
四、保存图片
var oldFilename = @"E:\环境部署\图片集\熊猫1.jpg";
var oldImage = System.Drawing.Image.FromFile(oldFilename);
var newFilename = @"E:\我的新熊猫.jpg";
oldImage.Save(newFilename, ImageFormat.Jpeg);
五、生成缩略图
/// <summary>
/// 生成图片缩略文件
/// </summary>
/// <param name="originalImage">图片源文件</param>
/// <param name="width">缩略图宽度</param>
/// <param name="height">缩略图高度</param>
/// <param name="mode">生成缩略图的方式</param>
/// <returns>缩率处理后图片文件</returns>
public static Image MakeThumbnail(Image originalImage, int width, int height, ThumbnailModel mode)
{
int towidth = width;
int toheight = height; int x = ;
int y = ;
int ow = originalImage.Width;
int oh = originalImage.Height; switch (mode)
{
case ThumbnailModel.HighWidth: //指定高宽缩放（可能变形）
break;
case ThumbnailModel.Width: //指定宽，高按比例
toheight = originalImage.Height * width / originalImage.Width;
break;
case ThumbnailModel.Hight: //指定高，宽按比例
towidth = originalImage.Width * height / originalImage.Height;
break;
case ThumbnailModel.Default: //指定高，宽按比例
if (ow <= towidth && oh <= toheight)
{
x = -(towidth - ow) / ;
y = -(toheight - oh) / ;
ow = towidth;
oh = toheight;
}
else
{
if (ow > oh)//宽大于高
{
x = ;
y = -(ow - oh) / ;
oh = ow;
}
else//高大于宽
{
y = ;
x = -(oh - ow) / ;
ow = oh;
}
}
break;
case ThumbnailModel.Auto:
if (originalImage.Width / originalImage.Height >= width / height)
{
if (originalImage.Width > width)
{
towidth = width;
toheight = (originalImage.Height * width) / originalImage.Width;
}
else
{
towidth = originalImage.Width;
toheight = originalImage.Height;
}
}
else
{
if (originalImage.Height > height)
{
toheight = height;
towidth = (originalImage.Width * height) / originalImage.Height;
}
else
{
towidth = originalImage.Width;
toheight = originalImage.Height;
}
}
break;
case ThumbnailModel.Cut: //指定高宽裁减（不变形）
if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
{
oh = originalImage.Height;
ow = originalImage.Height * towidth / toheight;
y = ;
x = (originalImage.Width - ow) / ;
}
else
{
ow = originalImage.Width;
oh = originalImage.Width * height / towidth;
x = ;
y = (originalImage.Height - oh) / ;
}
break;
default: break;
} //新建一个bmp图片
System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight); //新建一个画板
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap); //设置高质量插值法
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; //设置高质量,低速度呈现平滑程度
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; //清空画布并以透明背景色填充
g.Clear(System.Drawing.Color.White); //在指定位置并且按指定大小绘制原图片的指定部分
g.DrawImage(originalImage, new System.Drawing.Rectangle(, , towidth, toheight),
new System.Drawing.Rectangle(x, y, ow, oh),
System.Drawing.GraphicsUnit.Pixel); return bitmap;
}
其中缩略图模式定义如下：
/// <summary>
/// 缩率图处理模式
/// </summary>
public enum ThumbnailModel
{
/// <summary>
/// 指定高宽缩放（可能变形）
/// </summary>
HighWidth, /// <summary>
/// 指定宽，高按比例
/// </summary>
Width, /// <summary>
/// 默认 全图不变形
/// </summary>
Default, /// <summary>
/// 指定高，宽按比例
/// </summary>
Hight, /// <summary>
/// 指定高宽裁减（不变形）？？指定裁剪区域
/// </summary>
Cut, /// <summary>
/// 自动 原始图片按比例缩放
/// </summary>
Auto
}