最近做东西,客户要求上传商品大图,自动生成缩略图,要求等比缩放,正好能在指定的大小内显示,(即如果高超出的比宽超出的多,就把高缩到指定高度,宽也等比缩放,反之宽也如此)
从网上找了如下代码(出处不明),但发现他的生成缩略图的方式有四种,但都不是我想要的,于是在上面加了case "DB"://等比缩放（不变形，如果高大按高，宽大按宽缩放） 这种方式实现了我想要的功能
/**/
/// <summary>
/// 生成缩略图
/// </summary>
/// <param name="originalImagePath">源图路径（物理路径）</param>
/// <param name="thumbnailPath">缩略图路径（物理路径）</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>
public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode,string type)
{
System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);
int towidth = width;
int toheight = height;
int x = 0;
int y = 0;
int ow = originalImage.Width;
int oh = originalImage.Height;
switch (mode)
{
case "HW"://指定高宽缩放（可能变形）
break;
case "W"://指定宽，高按比例
toheight = originalImage.Height * width / originalImage.Width;
break;
case "H"://指定高，宽按比例
towidth = originalImage.Width * height / originalImage.Height;
break;
case "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 = 0;
x = (originalImage.Width - ow) / 2;
}
else
{
ow = originalImage.Width;
oh = originalImage.Width * height / towidth;
x = 0;
y = (originalImage.Height - oh) / 2;
}
break;
case "DB"://等比缩放（不变形，如果高大按高，宽大按宽缩放）
if ((double)originalImage.Width / (double)towidth < (double)originalImage.Height / (double)toheight)
{
toheight = height;
towidth = originalImage.Width * height / originalImage.Height;
}
else
{
towidth = width;
toheight = originalImage.Height * width / originalImage.Width;
}
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.Transparent);
//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(0, 0, towidth, toheight),
new System.Drawing.Rectangle(x, y, ow, oh),
System.Drawing.GraphicsUnit.Pixel);
try
{
//保存缩略图
if (type=="JPG")
{
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
}
if (type=="BMP")
{
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Bmp);
}
if (type=="GIF")
{
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Gif);
}
if (type=="PNG")
{
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Png);
}
}
catch (System.Exception e)
{
throw e;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}
}
/**/
/// <summary>
/// 在图片上增加文字水印
/// </summary>
/// <param name="Path">原服务器图片路径</param>
/// <param name="Path_sy">生成的带文字水印的图片路径</param>
protected void AddShuiYinWord(string Path, string Path_sy)
{
string addText = "测试水印";
System.Drawing.Image image = System.Drawing.Image.FromFile(Path);
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(image);
g.DrawImage(image, 0, 0, image.Width, image.Height);
System.Drawing.Font f = new System.Drawing.Font("Verdana", 16);
System.Drawing.Brush b = new System.Drawing.SolidBrush(System.Drawing.Color.Blue);
g.DrawString(addText, f, b, 15, 15);
g.Dispose();
image.Save(Path_sy);
image.Dispose();
}
/**/
/// <summary>
/// 在图片上生成图片水印
/// </summary>
/// <param name="Path">原服务器图片路径</param>
/// <param name="Path_syp">生成的带图片水印的图片路径</param>
/// <param name="Path_sypf">水印图片路径</param>
protected void AddShuiYinPic(string Path, string Path_syp, string Path_sypf)
{
System.Drawing.Image image = System.Drawing.Image.FromFile(Path);
System.Drawing.Image copyImage = System.Drawing.Image.FromFile(Path_sypf);
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(image);
g.DrawImage(copyImage, new System.Drawing.Rectangle(image.Width - copyImage.Width, image.Height - copyImage.Height, copyImage.Width, copyImage.Height), 0, 0, copyImage.Width, copyImage.Height, System.Drawing.GraphicsUnit.Pixel);
g.Dispose();
image.Save(Path_syp);
image.Dispose();
}
