asp.net C#图片缩放放大剪切代码

asp.net
C#图片缩放放大剪切代码

net c#图片缩放放大剪切代码

using system;
using system.collections.generic;
using system.text;
using system.io;
using system.drawing;
using system.drawing.drawing2d;
using system.drawing.imaging;

namespace wujian.common
{
/// <summary>
/// 图片处理类
/// </summary>
public class ptimage
{
#region 正方型裁剪并缩放
/// <summary>
/// 正方型裁剪
/// 以图片中心为轴心，截取正方型，然后等比缩放
/// 用于头像处理
/// </summary>
/// <param name="postedfile">原图httppostedfile对象</param>
/// <param name="filesaveurl">缩略图存放地址</param>
/// <param name="side">指定的边长（正方型）</param>
/// <param name="quality">质量（范围0-100）</param>
public static void cutforsquare(system.web.httppostedfile postedfile, string filesaveurl, int side, int quality)
{
//创建目录
string dir = path.getdirectoryname(filesaveurl);
if (!directory.exists(dir))
directory.createdirectory(dir);

//原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）
system.drawing.image initimage = system.drawing.image.fromstream(postedfile.inputstream, true);

//原图宽高均小于模版，不作处理，直接保存
if (initimage.width <= side && initimage.height <= side)
{
initimage.save(filesaveurl, system.drawing.imaging.imageformat.jpeg);
}
else
{
//原始图片的宽、高
int initwidth = initimage.width;
int initheight = initimage.height;

//非正方型先裁剪为正方型
if (initwidth != initheight)
{
//截图对象
system.drawing.image pickedimage = null;
system.drawing.graphics pickedg = null;

//宽大于高的横图
if (initwidth > initheight)
{
//对象实例化
pickedimage = new system.drawing.bitmap(initheight, initheight);
pickedg = system.drawing.graphics.fromimage(pickedimage);
//设置质量
pickedg.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
pickedg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
//定位
rectangle fromr = new rectangle((initwidth - initheight) / 2, 0, initheight, initheight);
rectangle tor = new rectangle(0, 0, initheight, initheight);
//画图
pickedg.drawimage(initimage, tor, fromr, system.drawing.graphicsunit.pixel);
//重置宽
initwidth = initheight;
}
//高大于宽的竖图
else
{
//对象实例化
pickedimage = new system.drawing.bitmap(initwidth, initwidth);
pickedg = system.drawing.graphics.fromimage(pickedimage);
//设置质量
pickedg.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
pickedg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
//定位
rectangle fromr = new rectangle(0, (initheight - initwidth) / 2, initwidth, initwidth);
rectangle tor = new rectangle(0, 0, initwidth, initwidth);
//画图
pickedg.drawimage(initimage, tor, fromr, system.drawing.graphicsunit.pixel);
//重置高
initheight = initwidth;
}

//将截图对象赋给原图
initimage = (system.drawing.image)pickedimage.clone();
//释放截图资源
pickedg.dispose();
pickedimage.dispose();
}

//缩略图对象
system.drawing.image resultimage = new system.drawing.bitmap(side, side);
system.drawing.graphics resultg = system.drawing.graphics.fromimage(resultimage);
//设置质量
resultg.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
resultg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
//用指定背景色清空画布
resultg.clear(color.white);
//绘制缩略图
resultg.drawimage(initimage, new system.drawing.rectangle(0, 0, side, side), new system.drawing.rectangle(0, 0, initwidth, initheight), system.drawing.graphicsunit.pixel);

//关键质量控制
//获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiff
imagecodecinfo[] icis = imagecodecinfo.getimageencoders();
imagecodecinfo ici = null;
foreach (imagecodecinfo i in icis)
{
if (i.mimetype == "image/jpeg" || i.mimetype == "image/bmp" || i.mimetype == "image/png" || i.mimetype == "image/gif")
{
ici = i;
}
}
encoderparameters ep = new encoderparameters(1);
ep.param[0] = new encoderparameter(system.drawing.imaging.encoder.quality, (long)quality);

//保存缩略图
resultimage.save(filesaveurl, ici, ep);

//释放关键质量控制所用资源
ep.dispose();

//释放缩略图资源
resultg.dispose();
resultimage.dispose();

//释放原始图片资源
initimage.dispose();
}
}

/// <summary>
/// 正方型裁剪
/// 以图片中心为轴心，截取正方型，然后等比缩放
/// 用于头像处理
/// </summary>
/// <param name="postedfile">原图httppostedfile对象</param>
/// <param name="filesaveurl">缩略图存放地址</param>
/// <param name="side">指定的边长（正方型）</param>
/// <param name="quality">质量（范围0-100）</param>
public static void cutforsquare(system.io.stream fromfile, string filesaveurl, int side, int quality)
{
//创建目录
string dir = path.getdirectoryname(filesaveurl);
if (!directory.exists(dir))
directory.createdirectory(dir);

//原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）
system.drawing.image initimage = system.drawing.image.fromstream(fromfile, true);

//原图宽高均小于模版，不作处理，直接保存
if (initimage.width <= side && initimage.height <= side)
{
initimage.save(filesaveurl, system.drawing.imaging.imageformat.jpeg);
}
else
{
//原始图片的宽、高
int initwidth = initimage.width;
int initheight = initimage.height;

//非正方型先裁剪为正方型
if (initwidth != initheight)
{
//截图对象
system.drawing.image pickedimage = null;
system.drawing.graphics pickedg = null;

//宽大于高的横图
if (initwidth > initheight)
{
//对象实例化
pickedimage = new system.drawing.bitmap(initheight, initheight);
pickedg = system.drawing.graphics.fromimage(pickedimage);
//设置质量
pickedg.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
pickedg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
//定位
rectangle fromr = new rectangle((initwidth - initheight) / 2, 0, initheight, initheight);
rectangle tor = new rectangle(0, 0, initheight, initheight);
//画图
pickedg.drawimage(initimage, tor, fromr, system.drawing.graphicsunit.pixel);
//重置宽
initwidth = initheight;
}
//高大于宽的竖图
else
{
//对象实例化
pickedimage = new system.drawing.bitmap(initwidth, initwidth);
pickedg = system.drawing.graphics.fromimage(pickedimage);
//设置质量
pickedg.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
pickedg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
//定位
rectangle fromr = new rectangle(0, (initheight - initwidth) / 2, initwidth, initwidth);
rectangle tor = new rectangle(0, 0, initwidth, initwidth);
//画图
pickedg.drawimage(initimage, tor, fromr, system.drawing.graphicsunit.pixel);
//重置高
initheight = initwidth;
}

//将截图对象赋给原图
initimage = (system.drawing.image)pickedimage.clone();
//释放截图资源
pickedg.dispose();
pickedimage.dispose();
}

//缩略图对象
system.drawing.image resultimage = new system.drawing.bitmap(side, side);
system.drawing.graphics resultg = system.drawing.graphics.fromimage(resultimage);
//设置质量
resultg.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
resultg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
//用指定背景色清空画布
resultg.clear(color.white);
//绘制缩略图
resultg.drawimage(initimage, new system.drawing.rectangle(0, 0, side, side), new system.drawing.rectangle(0, 0, initwidth, initheight), system.drawing.graphicsunit.pixel);

//关键质量控制
//获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiff
imagecodecinfo[] icis = imagecodecinfo.getimageencoders();
imagecodecinfo ici = null;
foreach (imagecodecinfo i in icis)
{
if (i.mimetype == "image/jpeg" || i.mimetype == "image/bmp" || i.mimetype == "image/png" || i.mimetype == "image/gif")
{
ici = i;
}
}
encoderparameters ep = new encoderparameters(1);
ep.param[0] = new encoderparameter(system.drawing.imaging.encoder.quality, (long)quality);

//保存缩略图
resultimage.save(filesaveurl, ici, ep);

//释放关键质量控制所用资源
ep.dispose();

//释放缩略图资源
resultg.dispose();
resultimage.dispose();

//释放原始图片资源
initimage.dispose();
}
}
#endregion

#region 固定模版裁剪并缩放
/// <summary>
/// 指定长宽裁剪
/// 按模版比例最大范围的裁剪图片并缩放至模版尺寸
/// </summary>
/// <param name="postedfile">原图httppostedfile对象</param>
/// <param name="filesaveurl">保存路径</param>
/// <param name="maxwidth">最大宽(单位:px)</param>
/// <param name="maxheight">最大高(单位:px)</param>
/// <param name="quality">质量（范围0-100）</param>
public static void cutforcustom(system.web.httppostedfile postedfile, string filesaveurl, int maxwidth, int maxheight, int quality)
{
//从文件获取原始图片，并使用流中嵌入的颜色管理信息
system.drawing.image initimage = system.drawing.image.fromstream(postedfile.inputstream, true);

//原图宽高均小于模版，不作处理，直接保存
if (initimage.width <= maxwidth && initimage.height <= maxheight)
{
initimage.save(filesaveurl, system.drawing.imaging.imageformat.jpeg);
}
else
{
//模版的宽高比例
double templaterate = (double)maxwidth / maxheight;
//原图片的宽高比例
double initrate = (double)initimage.width / initimage.height;

//原图与模版比例相等，直接缩放
if (templaterate == initrate)
{
//按模版大小生成最终图片
system.drawing.image templateimage = new system.drawing.bitmap(maxwidth, maxheight);
system.drawing.graphics templateg = system.drawing.graphics.fromimage(templateimage);
templateg.interpolationmode = system.drawing.drawing2d.interpolationmode.high;
templateg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
templateg.clear(color.white);
templateg.drawimage(initimage, new system.drawing.rectangle(0, 0, maxwidth, maxheight), new system.drawing.rectangle(0, 0, initimage.width, initimage.height), system.drawing.graphicsunit.pixel);
templateimage.save(filesaveurl, system.drawing.imaging.imageformat.jpeg);
}
//原图与模版比例不等，裁剪后缩放
else
{
//裁剪对象
system.drawing.image pickedimage = null;
system.drawing.graphics pickedg = null;

//定位
rectangle fromr = new rectangle(0, 0, 0, 0);//原图裁剪定位
rectangle tor = new rectangle(0, 0, 0, 0);//目标定位

//宽为标准进行裁剪
if (templaterate > initrate)
{
//裁剪对象实例化
pickedimage = new system.drawing.bitmap(initimage.width, (int)math.floor(initimage.width / templaterate));
pickedg = system.drawing.graphics.fromimage(pickedimage);

//裁剪源定位
fromr.x = 0;
fromr.y = (int)math.floor((initimage.height - initimage.width / templaterate) / 2);
fromr.width = initimage.width;
fromr.height = (int)math.floor(initimage.width / templaterate);

//裁剪目标定位
tor.x = 0;
tor.y = 0;
tor.width = initimage.width;
tor.height = (int)math.floor(initimage.width / templaterate);
}
//高为标准进行裁剪
else
{
pickedimage = new system.drawing.bitmap((int)math.floor(initimage.height * templaterate), initimage.height);
pickedg = system.drawing.graphics.fromimage(pickedimage);

fromr.x = (int)math.floor((initimage.width - initimage.height * templaterate) / 2);
fromr.y = 0;
fromr.width = (int)math.floor(initimage.height * templaterate);
fromr.height = initimage.height;

tor.x = 0;
tor.y = 0;
tor.width = (int)math.floor(initimage.height * templaterate);
tor.height = initimage.height;
}

//设置质量
pickedg.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
pickedg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;

//裁剪
pickedg.drawimage(initimage, tor, fromr, system.drawing.graphicsunit.pixel);

//按模版大小生成最终图片
system.drawing.image templateimage = new system.drawing.bitmap(maxwidth, maxheight);
system.drawing.graphics templateg = system.drawing.graphics.fromimage(templateimage);
templateg.interpolationmode = system.drawing.drawing2d.interpolationmode.high;
templateg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
templateg.clear(color.white);
templateg.drawimage(pickedimage, new system.drawing.rectangle(0, 0, maxwidth, maxheight), new system.drawing.rectangle(0, 0, pickedimage.width, pickedimage.height), system.drawing.graphicsunit.pixel);

//关键质量控制
//获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiff
imagecodecinfo[] icis = imagecodecinfo.getimageencoders();
imagecodecinfo ici = null;
foreach (imagecodecinfo i in icis)
{
if (i.mimetype == "image/jpeg" || i.mimetype == "image/bmp" || i.mimetype == "image/png" || i.mimetype == "image/gif")
{
ici = i;
}
}
encoderparameters ep = new encoderparameters(1);
ep.param[0] = new encoderparameter(system.drawing.imaging.encoder.quality, (long)quality);

//保存缩略图
templateimage.save(filesaveurl, ici, ep);
//templateimage.save(filesaveurl, system.drawing.imaging.imageformat.jpeg);

//释放资源
templateg.dispose();
templateimage.dispose();

pickedg.dispose();
pickedimage.dispose();
}
}

//释放资源
initimage.dispose();
}
#endregion

#region 等比缩放
/// <summary>
/// 图片等比缩放
/// </summary>
/// <param name="postedfile">原图httppostedfile对象</param>
/// <param name="savepath">缩略图存放地址</param>
/// <param name="targetwidth">指定的最大宽度</param>
/// <param name="targetheight">指定的最大高度</param>
/// <param name="watermarktext">水印文字(为""表示不使用水印)</param>
/// <param name="watermarkimage">水印图片路径(为""表示不使用水印)</param>
public static void zoomauto(system.web.httppostedfile postedfile, string savepath, system.double targetwidth, system.double targetheight, string watermarktext, string watermarkimage)
{
//创建目录
string dir = path.getdirectoryname(savepath);
if (!directory.exists(dir))
directory.createdirectory(dir);

//原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）
system.drawing.image initimage = system.drawing.image.fromstream(postedfile.inputstream, true);

//原图宽高均小于模版，不作处理，直接保存
if (initimage.width <= targetwidth && initimage.height <= targetheight)
{
//文字水印
if (watermarktext != "")
{
using (system.drawing.graphics gwater = system.drawing.graphics.fromimage(initimage))
{
system.drawing.font fontwater = new font("黑体", 10);
system.drawing.brush brushwater = new solidbrush(color.white);
gwater.drawstring(watermarktext, fontwater, brushwater, 10, 10);
gwater.dispose();
}
}

//透明图片水印
if (watermarkimage != "")
{
if (file.exists(watermarkimage))
{
//获取水印图片
using (system.drawing.image wrimage = system.drawing.image.fromfile(watermarkimage))
{
//水印绘制条件：原始图片宽高均大于或等于水印图片
if (initimage.width >= wrimage.width && initimage.height >= wrimage.height)
{
graphics gwater = graphics.fromimage(initimage);

//透明属性
imageattributes imgattributes = new imageattributes();
colormap colormap = new colormap();
colormap.oldcolor = color.fromargb(255, 0, 255, 0);
colormap.newcolor = color.fromargb(0, 0, 0, 0);
colormap[] remaptable = { colormap };
imgattributes.setremaptable(remaptable, coloradjusttype.bitmap);

float[][] colormatrixelements = {
new float[] {1.0f,  0.0f,  0.0f,  0.0f, 0.0f},
new float[] {0.0f,  1.0f,  0.0f,  0.0f, 0.0f},
new float[] {0.0f,  0.0f,  1.0f,  0.0f, 0.0f},
new float[] {0.0f,  0.0f,  0.0f,  0.5f, 0.0f},//透明度:0.5
new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}
};

colormatrix wmcolormatrix = new colormatrix(colormatrixelements);
imgattributes.setcolormatrix(wmcolormatrix, colormatrixflag.default, coloradjusttype.bitmap);
gwater.drawimage(wrimage, new rectangle(initimage.width - wrimage.width, initimage.height - wrimage.height, wrimage.width, wrimage.height), 0, 0, wrimage.width, wrimage.height, graphicsunit.pixel, imgattributes);

gwater.dispose();
}
wrimage.dispose();
}
}
}

//保存
initimage.save(savepath, system.drawing.imaging.imageformat.jpeg);
}
else
{
//缩略图宽、高计算
double newwidth = initimage.width;
double newheight = initimage.height;

//宽大于高或宽等于高（横图或正方）
if (initimage.width > initimage.height || initimage.width == initimage.height)
{
//如果宽大于模版
if (initimage.width > targetwidth)
{
//宽按模版，高按比例缩放
newwidth = targetwidth;
newheight = initimage.height * (targetwidth / initimage.width);
}
}
//高大于宽（竖图）
else
{
//如果高大于模版
if (initimage.height > targetheight)
{
//高按模版，宽按比例缩放
newheight = targetheight;
newwidth = initimage.width * (targetheight / initimage.height);
}
}

//生成新图
//新建一个bmp图片
system.drawing.image newimage = new system.drawing.bitmap((int)newwidth, (int)newheight);
//新建一个画板
system.drawing.graphics newg = system.drawing.graphics.fromimage(newimage);

//设置质量
newg.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
newg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;

//置背景色
newg.clear(color.white);
//画图
newg.drawimage(initimage, new system.drawing.rectangle(0, 0, newimage.width, newimage.height), new system.drawing.rectangle(0, 0, initimage.width, initimage.height), system.drawing.graphicsunit.pixel);

//文字水印
if (watermarktext != "")
{
using (system.drawing.graphics gwater = system.drawing.graphics.fromimage(newimage))
{
system.drawing.font fontwater = new font("宋体", 10);
system.drawing.brush brushwater = new solidbrush(color.white);
gwater.drawstring(watermarktext, fontwater, brushwater, 10, 10);
gwater.dispose();
}
}

//透明图片水印
if (watermarkimage != "")
{
if (file.exists(watermarkimage))
{
//获取水印图片
using (system.drawing.image wrimage = system.drawing.image.fromfile(watermarkimage))
{
//水印绘制条件：原始图片宽高均大于或等于水印图片
if (newimage.width >= wrimage.width && newimage.height >= wrimage.height)
{
graphics gwater = graphics.fromimage(newimage);

//透明属性
imageattributes imgattributes = new imageattributes();
colormap colormap = new colormap();
colormap.oldcolor = color.fromargb(255, 0, 255, 0);
colormap.newcolor = color.fromargb(0, 0, 0, 0);
colormap[] remaptable = { colormap };
imgattributes.setremaptable(remaptable, coloradjusttype.bitmap);

float[][] colormatrixelements = {
new float[] {1.0f,  0.0f,  0.0f,  0.0f, 0.0f},
new float[] {0.0f,  1.0f,  0.0f,  0.0f, 0.0f},
new float[] {0.0f,  0.0f,  1.0f,  0.0f, 0.0f},
new float[] {0.0f,  0.0f,  0.0f,  0.5f, 0.0f},//透明度:0.5
new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}
};

colormatrix wmcolormatrix = new colormatrix(colormatrixelements);
imgattributes.setcolormatrix(wmcolormatrix, colormatrixflag.default, coloradjusttype.bitmap);
gwater.drawimage(wrimage, new rectangle(newimage.width - wrimage.width, newimage.height - wrimage.height, wrimage.width, wrimage.height), 0, 0, wrimage.width, wrimage.height, graphicsunit.pixel, imgattributes);
gwater.dispose();
}
wrimage.dispose();
}
}
}

//保存缩略图
newimage.save(savepath, system.drawing.imaging.imageformat.jpeg);

//释放资源
newg.dispose();
newimage.dispose();
initimage.dispose();
}
}

#endregion

#region 其它
/// <summary>
/// 判断文件类型是否为web格式图片
/// (注：jpg,gif,bmp,png)
/// </summary>
/// <param name="contenttype">httppostedfile.contenttype</param>
/// <returns></returns>
public static bool iswebimage(string contenttype)
{
if (contenttype == "image/pjpeg" || contenttype == "image/jpeg" || contenttype == "image/gif" || contenttype == "image/bmp" || contenttype == "image/png")
{
return true;
}
else
{
return false;
}
}

#endregion
}//end class
}

比如相册功能，通常用户上传相片后我们都会针对该相片再生成一张缩略图，用于其它页面上的列表显示。随便看一下，大部分网站基 本都是将原图等比缩放来生成缩略图。但完美主义者会发现一些问题，比如显示排版时想让相片缩略图列表非常统一、整齐、和美观，比如要求每张缩略图大小固定 为120 x 90且不拉伸变形怎么办？再比如用户头像如何让缩略图比原图更清晰？或是如何在上传的图片下加一个半透明的logo水印？

ok，本文根据自己的项目代码描述以上问题的解决方案，所谓c#图片处理高级应用，感觉有点标题党了，这些功能并无多大技术含量。全部基于.net framework类库完成，代码中包含了c#图片处理的一些基础知识，与大家分享，个人能力有限，不足之处还请及时指正