asp.net下载图片时指定图片显示的大小

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
namespace Steam.Core
{
public static class ImageDeal
{
/**//// <summary>
/// 缩略图，按高度和宽度来缩略
///http://www.cnblogs.com/pooeo/
/// </summary>
/// <param name="image"></param>
/// <param name="size"></param>
/// <returns></returns>
public static Image Scale(Image image, Size size)
{
return image.GetThumbnailImage(size.Width, size.Height, null, new IntPtr());
}
/**//// <summary>
/// 缩略图，按倍数来缩略
///http://www.cnblogs.com/pooeo/
/// </summary>
/// <param name="image">原图</param>
/// <param name="multiple">放大或缩小的倍数，负数表示缩小，正数表示放大</param>
/// <returns></returns>
public static Image Scale(Image image, Int32 multiple)
{
Int32 newWidth;
Int32 newHeight;
Int32 absMultiple = Math.Abs(multiple);
if (multiple == 0)
{
return image.Clone() as Image;
}
if (multiple < 0)
{
newWidth = image.Width / absMultiple;
newHeight = image.Height / absMultiple;
}
else
{
newWidth = image.Width * absMultiple;
newHeight = image.Height * absMultiple;
}
return image.GetThumbnailImage(newWidth, newHeight, null, new IntPtr());
}
/**//// <summary>
/// 固定宽度缩略
///http://www.cnblogs.com/pooeo/
/// </summary>
/// <param name="image"></param>
/// <param name="width"></param>
/// <returns></returns>
public static Image ScaleFixWidth(Image image, Int32 width)
{
Int32 newWidth = width;
Int32 newHeight;
Double tempMultiple = (Double)newWidth / (Double)image.Width;
newHeight = (Int32)(((Double)image.Height) * tempMultiple);
Image newImage = new Bitmap(newWidth, newHeight);
using (Graphics newGp = Graphics.FromImage(newImage))
{
newGp.CompositingQuality = CompositingQuality.HighQuality;
//设置高质量插值法
newGp.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
//设置高质量,低速度呈现平滑程度
newGp.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//清空画布并以透明背景色填充
newGp.Clear(Color.Transparent);
newGp.DrawImage(image, new Rectangle(0, 0, newWidth, newHeight));
}
return newImage;
}
/**//// <summary>
/// 固定高度缩略
///http://www.cnblogs.com/pooeo/
/// </summary>
/// <param name="image"></param>
/// <param name="height"></param>
/// <returns></returns>
public static Image ScaleFixHeight(Image image, Int32 height)
{
Int32 newWidth;
Int32 newHeight = height;
Double tempMultiple = (Double)newHeight / (Double)image.Height;
newWidth = (Int32)(((Double)image.Width) * tempMultiple);
Image newImage = new Bitmap(newWidth, newHeight);
using (Graphics newGp = Graphics.FromImage(newImage))
{
newGp.CompositingQuality = CompositingQuality.HighQuality;
//设置高质量插值法
newGp.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
//设置高质量,低速度呈现平滑程度
newGp.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//清空画布并以透明背景色填充
newGp.Clear(Color.Transparent);
newGp.DrawImage(image, new Rectangle(0, 0, newWidth, newHeight));
}
return newImage;
}
/**//// <summary>
/// 裁减缩略，根据固定的高度和宽度
///http://www.cnblogs.com/pooeo/
/// </summary>
/// <param name="image"></param>
/// <param name="width"></param>
/// <param name="heigth"></param>
/// <returns></returns>
public static Image ScaleCut(Image image, Int32 width, Int32 height)
{
int x = 0;
int y = 0;
int ow = image.Width;
int oh = image.Height;
if (width >= ow && height >= oh)
{
return image;
}
//如果结果要比原来的宽
if (width > ow)
{
width = ow;
}
if (height > oh)
{
height = oh;
}
if ((double)image.Width / (double)image.Height > (double)width / (double)height)
{
oh = image.Height;
ow = image.Height * width / height;
y = 0;
x = (image.Width - ow) / 2;
}
else
{
ow = image.Width;
oh = image.Width * height / width;
x = 0;
y = (image.Height - oh) / 2;
}
Image newImage = new Bitmap(width, height);
using (Graphics newGp = Graphics.FromImage(newImage))
{
newGp.CompositingQuality = CompositingQuality.HighQuality;
//设置高质量插值法
newGp.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
//设置高质量,低速度呈现平滑程度
newGp.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//清空画布并以透明背景色填充
newGp.Clear(Color.Transparent);
newGp.DrawImage(image, new Rectangle(0, 0, width, height),
new Rectangle(x, y, ow, oh),
GraphicsUnit.Pixel);
}
return newImage;
}
/**//// <summary>
/// 生成缩略图
///http://www.cnblogs.com/pooeo/
/// </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)
{
Image originalImage = 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;
default:
break;
}
//新建一个bmp图片
Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
//新建一个画板
Graphics g = System.Drawing.Graphics.FromImage(bitmap);
//设置高质量插值法
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
//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(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 Rectangle(0, 0, towidth, toheight),
new Rectangle(x, y, ow, oh),
GraphicsUnit.Pixel);
try
{
//以jpg格式保存缩略图
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch (System.Exception e)
{
throw e;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}
}
/**//// <summary>
/// 打水印，在某一点
///http://www.cnblogs.com/pooeo/
/// </summary>
/// <param name="image"></param>
/// <param name="waterImagePath"></param>
/// <param name="p"></param>
public static void Makewater(Image image, String waterImagePath, Point p)
{
ImageDeal.Makewater(image, waterImagePath, p, ImagePosition.TopLeft);
}
public static void Makewater(Image image, String waterImagePath, Point p, ImagePosition imagePosition)
{
using (Image warterImage = Image.FromFile(waterImagePath))
{
using (Graphics newGp = Graphics.FromImage(image))
{
newGp.CompositingQuality = CompositingQuality.HighQuality;
//设置高质量插值法
newGp.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
//设置高质量,低速度呈现平滑程度
newGp.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
switch (imagePosition)
{
case ImagePosition.BottomLeft:
p.Y = image.Height - warterImage.Height - p.Y;
break;
case ImagePosition.TopRigth:
p.X = image.Width - warterImage.Width - p.X;
break;
case ImagePosition.BottomRight:
p.Y = image.Height - warterImage.Height - p.Y;
p.X = image.Width - warterImage.Width - p.X;
break;
}
newGp.DrawImage(warterImage, new Rectangle(p, new Size(warterImage.Width, warterImage.Height)));
}
}
}
public static void Makewater(Image image, String waterStr, Font font, Brush brush, Point p)
{
ImageDeal.Makewater(image, waterStr, font, brush, p, ImagePosition.TopLeft);
}
public static void Makewater(Image image, String waterStr, Font font, Brush brush, Point p, ImagePosition imagePosition)
{
using (Graphics newGp = Graphics.FromImage(image))
{
Int32 stringWidth;
Int32 stringHeight;
stringHeight = (int)font.Size;
stringWidth = (int)(((float)StringDeal.GetBitLength(waterStr) / (float)2) * (font.Size + 1));
newGp.CompositingQuality = CompositingQuality.HighQuality;
//设置高质量插值法
newGp.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
//设置高质量,低速度呈现平滑程度
newGp.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//文字抗锯齿
newGp.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
switch (imagePosition)
{
case ImagePosition.BottomLeft:
p.Y = image.Height - stringHeight - p.Y;
break;
case ImagePosition.TopRigth:
p.X = image.Width - stringWidth - p.X;
break;
case ImagePosition.BottomRight:
p.Y = image.Height - stringHeight - p.Y;
p.X = image.Width - stringWidth - p.X;
break;
}
newGp.DrawString(waterStr, font, brush, p);
}
}
/**//// <summary>
/// 高质量保存
///http://www.cnblogs.com/pooeo/
/// </summary>
/// <param name="image"></param>
/// <param name="path"></param>
public static void SaveQuality(Image image, String path)
{
ImageCodecInfo myImageCodecInfo;
Encoder myEncoder;
EncoderParameter myEncoderParameter;
EncoderParameters myEncoderParameters;
myImageCodecInfo = ImageCodecInfo.GetImageEncoders()[0];
myEncoder = Encoder.Quality;
myEncoderParameters = new EncoderParameters(1);
myEncoderParameter = new EncoderParameter(myEncoder, 100L); // 0-100
myEncoderParameters.Param[0] = myEncoderParameter;
try
{
image.Save(path, myImageCodecInfo, myEncoderParameters);
}
finally
{
myEncoderParameter.Dispose();
myEncoderParameters.Dispose();
}
}
}
public enum StringPosition
{
TopLeft,
BottomLeft
}
public enum ImagePosition
{
TopLeft,
BottomLeft,
BottomRight,
TopRigth
}
}

试试这个类吧。简单实用的using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Drawing;
/// <summary>
/// MakeThumbnails 的摘要说明
/// </summary>
public class MakeThumbnails
{
    public MakeThumbnails()
    {
    }
    /// <summary>
    /// 生成缩略图(最终图片固定大小,图片按比例缩小,并为缩略图加上边框,以jpg格式保存)
    /// </summary>
    /// <param name="sourceImg">原图片(物理路径)</param>
    /// <param name="toPath">缩略图存放地址(物理路径,带文件名)</param>
    /// <param name="width">缩略图宽度</param>
    /// <param name="height">缩略图高度</param>
    /// <param name="backColor">如果图片按比例缩小后不能填充满缩略图,则使用此颜色填充(比如"#FFFFFF")</param>
    /// <param name="borderColor">边框颜色(比如"#999999")</param>
    public static void MakePic(string sourceImg, string toPath, int width, int height, string backColor, string borderColor)
    {
        System.Drawing.Image originalImage = System.Drawing.Image.FromFile(sourceImg);
        int towidth = width;
        int toheight = height;
        int x = 0;
        int y = 0;
        int ow = originalImage.Width;
        int oh = originalImage.Height;
        string mode;
        if (ow < towidth && oh < toheight)//如果原图片大小小于指定的图片的宽度和高度　
        {
            towidth = ow;
            toheight = oh;
        }
        else
        {
            if (originalImage.Width / originalImage.Height >= width / height)
            {
                mode = "W";
            }
            else
            {
                mode = "H";
            }
            switch (mode)
            {
                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;
                default:
                    break;
            }
        }
        //新建一个bmp图片
        System.Drawing.Image bitmap = new System.Drawing.Bitmap(width, height);
        //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;
        //清空画布并以指定颜色填充
        g.Clear(ColorTranslator.FromHtml(backColor));
        //在指定位置并且按指定大小绘制原图片的指定部分
        int top = (height - toheight) / 2;
        int left = (width - towidth) / 2;
        g.DrawImage(originalImage, new System.Drawing.Rectangle(left, top, towidth, toheight),
        new System.Drawing.Rectangle(x, y, ow, oh),
        System.Drawing.GraphicsUnit.Pixel);
        Pen pen = new Pen(ColorTranslator.FromHtml(borderColor));
        g.DrawRectangle(pen, 0, 0, width - 1, height - 1);
        try
        {
            //以jpg格式保存缩略图
            bitmap.Save(toPath, System.Drawing.Imaging.ImageFormat.Jpeg);
        }
        catch (System.Exception e)
        {
            throw e;
        }
        finally
        {
            originalImage.Dispose();
            bitmap.Dispose();
            g.Dispose();
        }
    }
}

等比例缩放图片
public void SmallPic(string strOldPic, string strNewPic, int intWidth, int intHeight)
  {    System.Drawing.Bitmap objPic,objNewPic;
   try
   {
    objPic = new System.Drawing.Bitmap(strOldPic);
    objNewPic=new System.Drawing.Bitmap(objPic,intWidth,intHeight);
    objNewPic.Save(strNewPic);    }
   catch(Exception exp){throw exp;}
   finally
   {
    objPic=null;
    objNewPic=null;
   }
  }
  /// 按比例缩小图片，自动计算高度
  public void SmallPic(string strOldPic, string strNewPic, int intWidth)
  {    System.Drawing.Bitmap objPic,objNewPic;
   try
   {
    objPic = new System.Drawing.Bitmap(strOldPic);
    int intHeight=(intWidth / objPic.Width) * objPic.Height;
    objNewPic=new System.Drawing.Bitmap(objPic,intWidth,intHeight);
    objNewPic.Save(strNewPic);    }
   catch(Exception exp){throw exp;}
   finally
   {
    objPic=null;
    objNewPic=null;
   }
  }   /// 按比例缩小图片，自动计算宽度
  public void SmallPic(string strOldPic, string strNewPic, int intHeight)
  {    System.Drawing.Bitmap objPic,objNewPic;
   try
   {
    objPic = new System.Drawing.Bitmap(strOldPic);
    int intWidth=(intHeight / objPic.Height) * objPic.Width;
    objNewPic=new System.Drawing.Bitmap(objPic,intWidth,intHeight);
    objNewPic.Save(strNewPic);    }
   catch(Exception exp){throw exp;}
   finally
   {
    objPic=null;
    objNewPic=null;
   }
  }
参考

/// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="M_OriginalImagePath">源图路径（物理路径）</param>
        /// <param name="M_ThumbnailPath">缩略图路径（物理路径）</param>
        /// <param name="M_Width">缩略图宽度</param>
        /// <param name="M_Height">缩略图高度</param>
        public static  void MakeThumbnail(string M_OriginalImagePath, string M_ThumbnailPath, int M_Width, int M_Height)
        {
            System.Drawing.Image originalImage = System.Drawing.Image.FromFile(M_OriginalImagePath);            int towidth = 0;
            int toheight = 0;
            if (originalImage.Width >= M_Width && originalImage.Height <= M_Height)
            {
                towidth = M_Width;
                toheight = originalImage.Height;
            }            if (originalImage.Width <= M_Width && originalImage.Height >= M_Height)
            {
                towidth = originalImage.Width;
                toheight = M_Height;
            }
            if (originalImage.Width >= M_Width && originalImage.Height >= M_Height)
            {
                towidth = M_Width;
                toheight = M_Height;
            }
            if (originalImage.Width <= M_Width && originalImage.Height <= M_Height)
            {
                towidth = originalImage.Width;
                toheight = originalImage.Height;
            }
            int x = 0;//左上角的x坐标
            int y = 0;//左上角的y坐标
             //新建一个bmp图片
            System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
            //新建一个画板
            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(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, x, y, towidth, toheight);
            try
            {
                //以jpg格式保存缩略图
                bitmap.Save(M_ThumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            catch (System.Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }

调试易

asp.net下载图片时指定图片显示的大小

解决方案 »