Answers:
您可以Graphics.DrawImage用来将裁剪的图像从位图绘制到图形对象上。
Rectangle cropRect = new Rectangle(...);
Bitmap src = Image.FromFile(fileName) as Bitmap;
Bitmap target = new Bitmap(cropRect.Width, cropRect.Height);
using(Graphics g = Graphics.FromImage(target))
{
g.DrawImage(src, new Rectangle(0, 0, target.Width, target.Height),
cropRect,
GraphicsUnit.Pixel);
}DrawImageUnscaledAndClipped比DrawImage裁剪更有效？
查看此链接：http : //www.switchonthecode.com/tutorials/csharp-tutorial-image-editing-saving-cropping-and-reizing
private static Image cropImage(Image img, Rectangle cropArea)
{
Bitmap bmpImage = new Bitmap(img);
return bmpImage.Clone(cropArea, bmpImage.PixelFormat);
}比接受的答案简单的是：
public static Bitmap cropAtRect(this Bitmap b, Rectangle r)
{
using (Bitmap nb = new Bitmap(r.Width, r.Height))
using (Graphics g = Graphics.FromImage(nb))
{
g.DrawImage(b, -r.X, -r.Y);
return nb;
}
}并且避免了最简单答案的“ 内存不足 ”异常风险。
需要注意的是Bitmap和Graphics是IDisposable因此using条款。
编辑：我发现这对于使用Bitmap.Save或Paint.exe 保存的PNG 很好，但是对于使用例如Paint Shop Pro 6保存的PNG则失败-内容被替换了。加GraphicsUnit.Pixel给出不同的错误结果。这些失败的PNG也许只是错误的。
Bitmap和Graphics是IDisposable-增加一个using条款
用
bmp.SetResolution(image.HorizontalResolution, image .VerticalResolution);
即使您在此处实现最佳答案，也可能需要这样做，特别是当您的图像非常好并且分辨率不完全是96.0时
我的测试示例：
static Bitmap LoadImage()
{
return (Bitmap)Bitmap.FromFile( @"e:\Tests\d_bigImage.bmp" ); // here is large image 9222x9222 pixels and 95.96 dpi resolutions
}
static void TestBigImagePartDrawing()
{
using( var absentRectangleImage = LoadImage() )
{
using( var currentTile = new Bitmap( 256, 256 ) )
{
currentTile.SetResolution(absentRectangleImage.HorizontalResolution, absentRectangleImage.VerticalResolution);
using( var currentTileGraphics = Graphics.FromImage( currentTile ) )
{
currentTileGraphics.Clear( Color.Black );
var absentRectangleArea = new Rectangle( 3, 8963, 256, 256 );
currentTileGraphics.DrawImage( absentRectangleImage, 0, 0, absentRectangleArea, GraphicsUnit.Pixel );
}
currentTile.Save(@"e:\Tests\Tile.bmp");
}
}
}这是裁剪图像的简单示例
public Image Crop(string img, int width, int height, int x, int y)
{
try
{
Image image = Image.FromFile(img);
Bitmap bmp = new Bitmap(width, height, PixelFormat.Format24bppRgb);
bmp.SetResolution(80, 60);
Graphics gfx = Graphics.FromImage(bmp);
gfx.SmoothingMode = SmoothingMode.AntiAlias;
gfx.InterpolationMode = InterpolationMode.HighQualityBicubic;
gfx.PixelOffsetMode = PixelOffsetMode.HighQuality;
gfx.DrawImage(image, new Rectangle(0, 0, width, height), x, y, width, height, GraphicsUnit.Pixel);
// Dispose to free up resources
image.Dispose();
bmp.Dispose();
gfx.Dispose();
return bmp;
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
return null;
}
}如果您使用的是AForge.NET：
using(var croppedBitmap = new Crop(new Rectangle(10, 10, 10, 10)).Apply(bitmap))
{
// ...
}我一直在寻找一个简单且快速的功能，而没有其他库来完成这项工作。我尝试使用Nicks解决方案，但是我需要29.4秒的时间才能“提取” 1195张地图集文件的图像。因此，后来我以这种方式进行管理，并且需要2.43秒才能完成相同的工作。也许这会有所帮助。
// content of the Texture class
public class Texture
{
//name of the texture
public string name { get; set; }
//x position of the texture in the atlas image
public int x { get; set; }
//y position of the texture in the atlas image
public int y { get; set; }
//width of the texture in the atlas image
public int width { get; set; }
//height of the texture in the atlas image
public int height { get; set; }
}
Bitmap atlasImage = new Bitmap(@"C:\somepicture.png");
PixelFormat pixelFormat = atlasImage.PixelFormat;
foreach (Texture t in textureList)
{
try
{
CroppedImage = new Bitmap(t.width, t.height, pixelFormat);
// copy pixels over to avoid antialiasing or any other side effects of drawing
// the subimages to the output image using Graphics
for (int x = 0; x < t.width; x++)
for (int y = 0; y < t.height; y++)
CroppedImage.SetPixel(x, y, atlasImage.GetPixel(t.x + x, t.y + y));
CroppedImage.Save(Path.Combine(workingFolder, t.name + ".png"), ImageFormat.Png);
}
catch (Exception ex)
{
// handle the exception
}
}使用C＃裁剪图像非常容易。但是，做这些事情将如何管理图像的裁剪会有些困难。
下面的示例是如何在C＃中裁剪图像的方法。
var filename = @"c:\personal\images\horizon.png";
var img = Image.FromFile(filename);
var rect = new Rectangle(new Point(0, 0), img.Size);
var cloned = new Bitmap(img).Clone(rect, img.PixelFormat);
var bitmap = new Bitmap(cloned, new Size(50, 50));
cloned.Dispose();有一个用于C＃包装的开源程序，托管在Codeplex上，称为Web Image Cropping。
注册控件
<%@ Register Assembly="CS.Web.UI.CropImage" Namespace="CS.Web.UI" TagPrefix="cs" %>
调整大小
<asp:Image ID="Image1" runat="server" ImageUrl="images/328.jpg" />
<cs:CropImage ID="wci1" runat="server" Image="Image1"
X="10" Y="10" X2="50" Y2="50" />在后面的代码中裁剪 -例如，单击按钮时调用Crop方法；
wci1.Crop(Server.MapPath("images/sample1.jpg"));
假设您想获取图像文件（JPEG，BMP，TIFF等）并裁剪，然后将其保存为较小的图像文件，建议您使用具有.NET API的第三方工具。以下是一些我喜欢的热门：
只有这个示例可以正常工作：
var crop = new Rectangle(0, y, bitmap.Width, h);
var bmp = new Bitmap(bitmap.Width, h);
var tempfile = Application.StartupPath+"\\"+"TEMP"+"\\"+Path.GetRandomFileName();
using (var gr = Graphics.FromImage(bmp))
{
try
{
var dest = new Rectangle(0, 0, bitmap.Width, h);
gr.DrawImage(image,dest , crop, GraphicsUnit.Point);
bmp.Save(tempfile,ImageFormat.Jpeg);
bmp.Dispose();
}
catch (Exception)
{
}
}这是另一种方式。就我而言，我有：
在按钮内部，我有以下代码：
Image myImage = Image.FromFile(@"C:\imagenes\myImage.gif");
Bitmap croppedBitmap = new Bitmap(myImage);
croppedBitmap = croppedBitmap.Clone(
new Rectangle(
(int)LeftMargin.Value, (int)TopMargin.Value,
myImage.Width - (int)LeftMargin.Value,
myImage.Height - (int)TopMargin.Value),
System.Drawing.Imaging.PixelFormat.DontCare);
pictureBox1.Image = croppedBitmap;我在Visual Studio 2012中使用C＃进行了尝试。我从此页面找到了此解决方案
这是在github上工作的演示
https://github.com/SystematixIndore/Crop-SaveImageInCSharp
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplication1.WebForm1" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<link href="css/jquery.Jcrop.css" rel="stylesheet" type="text/css" />
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3/jquery.min.js"></script>
<script type="text/javascript" src="js/jquery.Jcrop.js"></script>
</head>
<body>
<form id="form2" runat="server">
<div>
<asp:Panel ID="pnlUpload" runat="server">
<asp:FileUpload ID="Upload" runat="server" />
<br />
<asp:Button ID="btnUpload" runat="server" OnClick="btnUpload_Click" Text="Upload" />
<asp:Label ID="lblError" runat="server" Visible="false" />
</asp:Panel>
<asp:Panel ID="pnlCrop" runat="server" Visible="false">
<asp:Image ID="imgCrop" runat="server" />
<br />
<asp:HiddenField ID="X" runat="server" />
<asp:HiddenField ID="Y" runat="server" />
<asp:HiddenField ID="W" runat="server" />
<asp:HiddenField ID="H" runat="server" />
<asp:Button ID="btnCrop" runat="server" Text="Crop" OnClick="btnCrop_Click" />
</asp:Panel>
<asp:Panel ID="pnlCropped" runat="server" Visible="false">
<asp:Image ID="imgCropped" runat="server" />
</asp:Panel>
</div>
</form>
<script type="text/javascript">
jQuery(document).ready(function() {
jQuery('#imgCrop').Jcrop({
onSelect: storeCoords
});
});
function storeCoords(c) {
jQuery('#X').val(c.x);
jQuery('#Y').val(c.y);
jQuery('#W').val(c.w);
jQuery('#H').val(c.h);
};
</script>
</body>
</html>用于上传和裁剪的C＃代码逻辑。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;
using SD = System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;
namespace WebApplication1
{
public partial class WebForm1 : System.Web.UI.Page
{
String path = HttpContext.Current.Request.PhysicalApplicationPath + "images\\";
protected void Page_Load(object sender, EventArgs e)
{
}
protected void btnUpload_Click(object sender, EventArgs e)
{
Boolean FileOK = false;
Boolean FileSaved = false;
if (Upload.HasFile)
{
Session["WorkingImage"] = Upload.FileName;
String FileExtension = Path.GetExtension(Session["WorkingImage"].ToString()).ToLower();
String[] allowedExtensions = { ".png", ".jpeg", ".jpg", ".gif" };
for (int i = 0; i < allowedExtensions.Length; i++)
{
if (FileExtension == allowedExtensions[i])
{
FileOK = true;
}
}
}
if (FileOK)
{
try
{
Upload.PostedFile.SaveAs(path + Session["WorkingImage"]);
FileSaved = true;
}
catch (Exception ex)
{
lblError.Text = "File could not be uploaded." + ex.Message.ToString();
lblError.Visible = true;
FileSaved = false;
}
}
else
{
lblError.Text = "Cannot accept files of this type.";
lblError.Visible = true;
}
if (FileSaved)
{
pnlUpload.Visible = false;
pnlCrop.Visible = true;
imgCrop.ImageUrl = "images/" + Session["WorkingImage"].ToString();
}
}
protected void btnCrop_Click(object sender, EventArgs e)
{
string ImageName = Session["WorkingImage"].ToString();
int w = Convert.ToInt32(W.Value);
int h = Convert.ToInt32(H.Value);
int x = Convert.ToInt32(X.Value);
int y = Convert.ToInt32(Y.Value);
byte[] CropImage = Crop(path + ImageName, w, h, x, y);
using (MemoryStream ms = new MemoryStream(CropImage, 0, CropImage.Length))
{
ms.Write(CropImage, 0, CropImage.Length);
using (SD.Image CroppedImage = SD.Image.FromStream(ms, true))
{
string SaveTo = path + "crop" + ImageName;
CroppedImage.Save(SaveTo, CroppedImage.RawFormat);
pnlCrop.Visible = false;
pnlCropped.Visible = true;
imgCropped.ImageUrl = "images/crop" + ImageName;
}
}
}
static byte[] Crop(string Img, int Width, int Height, int X, int Y)
{
try
{
using (SD.Image OriginalImage = SD.Image.FromFile(Img))
{
using (SD.Bitmap bmp = new SD.Bitmap(Width, Height))
{
bmp.SetResolution(OriginalImage.HorizontalResolution, OriginalImage.VerticalResolution);
using (SD.Graphics Graphic = SD.Graphics.FromImage(bmp))
{
Graphic.SmoothingMode = SmoothingMode.AntiAlias;
Graphic.InterpolationMode = InterpolationMode.HighQualityBicubic;
Graphic.PixelOffsetMode = PixelOffsetMode.HighQuality;
Graphic.DrawImage(OriginalImage, new SD.Rectangle(0, 0, Width, Height), X, Y, Width, Height, SD.GraphicsUnit.Pixel);
MemoryStream ms = new MemoryStream();
bmp.Save(ms, OriginalImage.RawFormat);
return ms.GetBuffer();
}
}
}
}
catch (Exception Ex)
{
throw (Ex);
}
}
}
}