public static Byte[] GetnerateThumnail(int width, int height, ThumbnailGenMode mode, Byte[] oriImgByte)
{
byte[] result = null;
using (var stream = new MemoryStream(oriImgByte))
{
var oriImg = Image.FromStream(stream);
var waterMarkedImg = getnerateThumnail(width, height, mode, oriImg);
using (MemoryStream ms = new MemoryStream())
{
waterMarkedImg.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
result = ms.ToArray();
}
}
return(result);
}
private static Image getnerateThumnail(int width, int height, ThumbnailGenMode mode, System.Drawing.Image originalImage)
{
int towidth = width;
int toheight = height;
int x = 0;
int y = 0;
int ow = originalImage.Width;
int oh = originalImage.Height;
switch (mode)
{
case ThumbnailGenMode.HW: //指定高宽缩放（可能变形）
break;
case ThumbnailGenMode.W: //指定宽，高按比例
toheight = originalImage.Height * width / originalImage.Width;
break;
case ThumbnailGenMode.H: //指定高，宽按比例
towidth = originalImage.Width * height / originalImage.Height;
break;
case ThumbnailGenMode.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 ThumbnailGenMode.Auto: //自动调整
// 根据源图及欲生成的缩略图尺寸,计算缩略图的实际尺寸及其在"画布"上的位置
if (toheight * originalImage.Width > towidth * originalImage.Height)
{
toheight = originalImage.Height * width / originalImage.Width;
y = (height - toheight) / 2;
}
else
{
towidth = originalImage.Width * height / originalImage.Height;
x = (width - towidth) / 2;
}
break;
case ThumbnailGenMode.Exiu:
// 宽高都小于原图
if (width <= originalImage.Width && height <= originalImage.Height || width > originalImage.Width && height > originalImage.Height)
{
// 以缩放比最小的为准
if ((double)width / (double)originalImage.Width < (double)height / (double)originalImage.Height)
{
toheight = originalImage.Height * width / originalImage.Width;
}
else
{
towidth = originalImage.Width * height / originalImage.Height;
}
}
// 宽度较小原图的
if (width <= originalImage.Width && height > originalImage.Height)
{
towidth = originalImage.Width * height / originalImage.Height;
}
// 高度较小的
if (width > originalImage.Width && height <= originalImage.Height)
{
toheight = originalImage.Height * width / originalImage.Width;
}
break;
default:
break;
}
Image bitmap = null;
if (mode == ThumbnailGenMode.Auto)
{
bitmap = new System.Drawing.Bitmap(width, height);
}
else
{
bitmap = new System.Drawing.Bitmap(towidth, toheight);
}
//新建一个画板
using (var 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);
if (mode == ThumbnailGenMode.Auto)
{
// 指定高质量的双三次插值法。执行预筛选以确保高质量的收缩。此模式可产生质量最高的转换图像。
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
g.DrawImage(originalImage, new Rectangle(x, y, towidth, toheight), new Rectangle(0, 0, ow, oh), GraphicsUnit.Pixel);
}
else
{
//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 Rectangle(0, 0, towidth, toheight), new Rectangle(x, y, ow, oh), GraphicsUnit.Pixel);
}
}
return(bitmap);
}
/// <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, ThumbnailGenMode mode)
{
using (var originalImage = System.Drawing.Image.FromFile(originalImagePath))
{
using (var bitmap = getnerateThumnail(width, height, mode, originalImage))
{
//以jpg格式保存缩略图
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
}
}
}