相关文件下载：
1. 给图片添加水印的类库（dll)文件：ImageHandler.dll (18.00 kb)
2. 整个类库项目文件：ImageHandler.rar (45.03 kb)
摘要：
本文提供了一个给图片添加水印的C#类库，首先介绍了它的使用方法，其次介绍了该类库的结构，最后公开了它的源代码以及整个项目文件。
简介：
上篇文章介绍了使用C#及GDI+技术给图片添加水印的原理和技术细节。本文使用其技术做底层实现，采用模板设计模式架构，提供了一个高复用性与易扩展的图片处理类库。
一、类库的使用：
将类库(ImageHandler.dll (18.00 kb))复制到你的工程Bin文件夹后，在你的代码中添加zizhujy.ImageHandler命名空间，然后打开你要添加水印的图片，实例化一个zizhujy.ImageHandler中的Watermarker类，添加你想要的水印，完毕。就是如此简单！它可以被引用到Windows Console Application、Windows Form Application、Web Application、Web Service Application 等等工程中，以下以ASP.NET MVC 3 Application为例，就文字水印与图片水印分别列出三个代码实例。
1. 添加文字水印：
代码：
using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; using System.Drawing; using System.Drawing.Drawing2D; using System.Drawing.Imaging; using zizhujy.ImageHandler;
namespace zizhujy.Controllers { public class TestController : Controller { public void AddWatermark() { Image originImage = Image.FromFile(@"C:\source.jpg"); TextWatermarker txtWatermarker = new TextWatermarker(originImage, "www.zizhujy.com"); txtWatermarker.AddWatermark();
// Response and show the watermarked image in the browser
Response.ContentType = "image/jpeg";
txtWatermarker.WatermarkedImage.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
txtWatermarker.Dispose();
originImage.Dispose();
}
}
}
效果：
2. 添加图片水印：
代码：
using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; using System.Drawing; using System.Drawing.Drawing2D; using System.Drawing.Imaging; using zizhujy.ImageHandler;
namespace zizhujy.Controllers { public class TestController : Controller { public void AddWatermark() { Image originImage = Image.FromFile(@"C:\source.jpg"); Image watermark = Image.FromFile(@"C:\clock.png");
ImageWatermarker imgWatermarker = new ImageWatermarker(originImage, watermark);
imgWatermarker.AddWatermark();
// Response and show the watermarked image in the browser
Response.ContentType = "image/jpeg";
imgWatermarker.WatermarkedImage.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
imgWatermarker.Dispose();
watermark.Dispose();
originImage.Dispose();
}
}
}
效果：
3. 同时添加图片水印和文字水印：
代码：
using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; using System.Drawing; using System.Drawing.Drawing2D; using System.Drawing.Imaging; using zizhujy.ImageHandler;
namespace zizhujy.Controllers { public class TestController : Controller { public void AddWatermark() { // First, add the image watermark Image originImage = Image.FromFile(@"C:\source.jpg"); Image watermark = Image.FromFile(@"C:\clock.png");
ImageWatermarker imgWatermarker = new ImageWatermarker(originImage, watermark);
// You can set the watermark size, if you not then the watermark will be its original size by default
imgWatermarker.SetWatermarkHeight(80);
imgWatermarker.AddWatermark();
// Second, add the text watermark
TextWatermarker txtWatermarker = new TextWatermarker(imgWatermarker.WatermarkedImage, "<em class="text_cor1">www.zizhujy.com</em>");
// You can set the position of the watermark
txtWatermarker.Position = WatermarkPostion.TopLeft;
txtWatermarker.AddWatermark();
// Response and show the watermarked image in the browser
Response.ContentType = "image/jpeg";
// Note: save the secondly watermarked image
// (txtWatermarker not imgWatermarker because the txtWatermarker comes after than imgWatermarker)
txtWatermarker.WatermarkedImage.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
imgWatermarker.Dispose();
watermark.Dispose();
originImage.Dispose();
}
}
}
效果：
二、类库的结构(设计模式)
此类库采用了模板设计模式。因为对于给图片加水印，至少分为文本水印、图片水印两种。而不同的水印，将其添加到图片上的算法是一样的。即
- 获取源图片
- 获取水印
- 计算水印的位置Point (x,y)
- 计算水印的大小Size (width, height)
- 在源图片的Point位置处，以Size尺寸，将水印绘制出来，并返回新的图片
因此很自然想到使用模板设计模式，将以上算法封装在模板类Watermarker类中。对于图片水印与文本水印如何添加到源图片上，其方法是不一样的（详见上篇文章说明），故上述第5步，绘制水印的方法应该是抽象的，由具体的类来给予实现，即分别在ImageWatermarker和TextWatermarker中实现。
类图结构如下：
很简单明了，后面三个Enum是用来表示水印在源图片上出现的位置的struct结构体。
以下分别看每个类的结构：
三、类库的源码
先看模板类Watermarker.cs的源码（三个Enum结构体的代码也在这个文件中）：
using System; using System.Drawing;
namespace zizhujy.ImageHandler { /// /// Watermarker Template class /// public abstract class Watermarker : IDisposable { #region Properties
private Image originImage;
public Image OriginImage
{
get
{
return originImage;
}
set
{
originImage = value;
}
}
private Image watermarkedImage;
public Image WatermarkedImage
{
get
{
return watermarkedImage;
}
set
{
watermarkedImage = value;
}
}
private SizeF watermarkSize;
protected SizeF WatermarkSize
{
get
{
return watermarkSize;
}
set
{
watermarkSize = value;
}
}
private float x;
protected float X
{
get
{
return x;
}
set
{
x = value;
}
}
private float y;
protected float Y
{
get
{
return y;
}
set
{
y = value;
}
}
private bool computeX = true;
public bool ComputeX
{
get { return computeX; }
}
private bool computeY = true;
public bool ComputeY
{
get { return computeY; }
}
private WatermarkHorizontalPostion hPos;
public WatermarkHorizontalPostion HorizontalPosition
{
get
{
return hPos;
}
set
{
computeX = true;
hPos = value;
}
}
private WatermarkVerticalPostion vPos;
public WatermarkVerticalPostion VerticalPosition
{
get
{
return vPos;
}
set
{
computeY = true;
vPos = value;
}
}
public WatermarkPostion Position
{
get
{
return GetPosition(this.HorizontalPosition , this.VerticalPosition) ;
}
set
{
this.HorizontalPosition = GetHorizentalPosition(value);
this.VerticalPosition = GetVerticalPosition(value);
}
}
private int hMarginPixel;
public int HorizontalMarginPixel
{
get
{
return hMarginPixel;
}
set
{
hMarginPixel = value;
}
}
private int vMarginPixel;
public int VerticalMarginPixel
{
get
{
return vMarginPixel;
}
set
{
vMarginPixel = value;
}
}
public double HorizontalMarginPercent
{
get
{
return this.HorizontalMarginPixel / this.OriginImage.Width;
}
set
{
double percent = value > 1 ? 1 : (value < 0 ? 0 : value);
this.HorizontalMarginPixel = (int)(this.OriginImage.Width * percent);
}
}
public double VerticalMarginPercent
{
get
{
return this.VerticalMarginPixel / this.OriginImage.Height;
}
set
{
double percent = value > 1 ? 1 : (value < 0 ? 0 : value);
this.VerticalMarginPixel = (int)(this.originImage.Height * percent);
}
}
private Color shadowColor;
public Color ShadowColor
{
get
{
return shadowColor;
}
set
{
shadowColor = value;
}
}
private Color foreColor;
public Color ForeColor
{
get
{
return foreColor;
}
set
{
foreColor = value;
}
}
public double ShadowOpacity
{
get
{
return shadowColor.A / 255;
}
set
{
double percent = value > 1 ? 1 : (value < 0 ? 0 : value);
int alpha = (int)(255 * percent);
shadowColor = Color.FromArgb(alpha, shadowColor);
}
}
public virtual double ForegroundOpacity
{
get
{
return foreColor.A / 255;
}
set
{
double percent = value > 1 ? 1 : (value < 0 ? 0 : value);
int alpha = (int)(255 * percent);
foreColor = Color.FromArgb(alpha, foreColor);
}
}
private int shadowOffsetX;
public int ShadowOffsetX
{
get
{
return shadowOffsetX;
}
set
{
shadowOffsetX = value;
}
}
private int shadowOffsetY;
public int ShadowOffsetY
{
get
{
return shadowOffsetY;
}
set
{
shadowOffsetY = value;
}
}
#endregion
#region Contructor
public Watermarker(Image originImage)
{
this.OriginImage = originImage;
// 默认值
this.ShadowColor = Color.FromArgb(153, 0, 0, 0);
this.ForeColor = Color.FromArgb(153, 255, 255, 255);
this.ShadowOffsetX = 1;
this.ShadowOffsetY = 1;
this.Position = WatermarkPostion.BottomRight;
this.HorizontalMarginPixel = 10;
this.VerticalMarginPixel = 10;
}
#endregion
#region Methods
public void SetX(float x)
{
this.X = x;
computeX = false;
}
public void SetY(float y)
{
this.Y = y;
computeY = false;
}
public void SetXY(float x, float y)
{
SetX(x);
SetY(y);
}
///
/// Add water mark to original image
///
public Image AddWatermark()
{
ComputeWatermarkSize();
UpdateXY();
watermarkedImage = AddWatermarkToOriginImage();
return watermarkedImage;
}
///
/// hook
///
///
protected virtual SizeF ComputeWatermarkSize()
{
this.WatermarkSize = new SizeF(100f, 50f);
return this.WatermarkSize;
}
///
/// hook
///
protected virtual Image AddWatermarkToOriginImage()
{
return originImage;
}
///
/// hook
///
protected virtual void UpdateXY()
{
if (this.ComputeX)
{
switch (this.HorizontalPosition)
{
case WatermarkHorizontalPostion.Left:
this.X = this.HorizontalMarginPixel;
break;
case WatermarkHorizontalPostion.Center:
this.X = this.OriginImage.Width / 2 - this.WatermarkSize.Width / 2;
break;
case WatermarkHorizontalPostion.Right:
this.X = (this.OriginImage.Width - this.HorizontalMarginPixel - this.WatermarkSize.Width);
break;
default:
break;
}
}
if (this.ComputeY)
{
switch (this.VerticalPosition)
{
case WatermarkVerticalPostion.Top:
this.Y = this.VerticalMarginPixel;
break;
case WatermarkVerticalPostion.Middle:
this.Y = this.OriginImage.Height / 2 - this.WatermarkSize.Height / 2;
break;
case WatermarkVerticalPostion.Bottom:
this.Y = (this.OriginImage.Height - this.VerticalMarginPixel - this.WatermarkSize.Height);
break;
default:
break;
}
}
}
private static WatermarkHorizontalPostion GetHorizentalPosition(WatermarkPostion pos)
{
// Mask: 000 111
return (WatermarkHorizontalPostion)((char)pos & (char)0x07);
}
private static WatermarkVerticalPostion GetVerticalPosition(WatermarkPostion pos)
{
// Mask: 111 000
return (WatermarkVerticalPostion)((char)pos & (char)0x38);
}
private static WatermarkPostion GetPosition(WatermarkHorizontalPostion hPos, WatermarkVerticalPostion vPos)
{
return (WatermarkPostion)((char)hPos | (char)vPos);
}
#endregion
#region IDisposable 成员
public virtual void Dispose()
{
this.OriginImage.Dispose();
this.WatermarkedImage.Dispose();
}
#endregion
}
public enum WatermarkPostion
{
TopLeft = 0x24, // 100 100
TopCenter = 0x22, // 100 010
TopRight = 0x21, // 100 001
MiddleLeft = 0x14, // 010 100
MiddleCenter = 0x12, // 010 010
MiddleRight = 0x11, // 010 001
BottomLeft = 0x0C, // 001 100
BottomCenter = 0x0A, // 001 010
BottomRight = 0x09, // 001 001
}
public enum WatermarkHorizontalPostion
{
Left = 0x04, // 000 100
Center = 0x02, // 000 010
Right = 0x01, // 000 001
}
public enum WatermarkVerticalPostion
{
Top = 0x20, // 100 000
Middle = 0x10, // 010 000
Bottom = 0x08, // 001 000
}
}
再来分别看加图片水印的类ImageWatermarker.cs与加文本水印的类TextWatermark.cs的源码：
using System; using System.Collections.Generic; using System.Drawing; using System.Drawing.Imaging;namespace zizhujy.ImageHandler { public class ImageWatermarker : Watermarker { #region Properties
private Image watermarkImage; public Image WatermarkImage { get { return watermarkImage; } set { watermarkImage =value; } } private ImageAttributes imageAttributes = new ImageAttributes(); public ImageAttributes ImageAttributes { get { return imageAttributes; } set { imageAttributes = value; } } private List colorMaps = new List(); public List ColorMaps { get { return colorMaps; } set { colorMaps = value; } } public float[][] ColorMatrixElements { get { if (this.ColorMatrix != null) { return new float[][] { new float[] {this.ColorMatrix.Matrix00, this.ColorMatrix.Matrix01, this.ColorMatrix.Matrix02, this.ColorMatrix.Matrix03, this.ColorMatrix.Matrix04}, new float[] {this.ColorMatrix.Matrix10, this.ColorMatrix.Matrix11, this.ColorMatrix.Matrix12, this.ColorMatrix.Matrix13, this.ColorMatrix.Matrix14}, new float[] {this.ColorMatrix.Matrix20, this.ColorMatrix.Matrix21, this.ColorMatrix.Matrix22, this.ColorMatrix.Matrix23, this.ColorMatrix.Matrix24}, new float[] {this.ColorMatrix.Matrix30, this.ColorMatrix.Matrix31, this.ColorMatrix.Matrix32, this.ColorMatrix.Matrix33, this.ColorMatrix.Matrix34}, new float[] {this.ColorMatrix.Matrix40, this.ColorMatrix.Matrix41, this.ColorMatrix.Matrix42, this.ColorMatrix.Matrix43, this.ColorMatrix.Matrix44} }; } else { return null; } } set { this.ColorMatrix.Matrix00 = value[0][0]; this.ColorMatrix.Matrix01 = value[0][1]; this.ColorMatrix.Matrix02 = value[0][2]; this.ColorMatrix.Matrix03 = value[0][3]; this.ColorMatrix.Matrix04 = value[0][4]; this.ColorMatrix.Matrix10 = value[1][0]; this.ColorMatrix.Matrix11 = value[1][1]; this.ColorMatrix.Matrix12 = value[1][2]; this.ColorMatrix.Matrix13 = value[1][3]; this.ColorMatrix.Matrix14 = value[1][4]; this.ColorMatrix.Matrix20 = value[2][0]; this.ColorMatrix.Matrix21 = value[2][1]; this.ColorMatrix.Matrix22 = value[2][2]; this.ColorMatrix.Matrix23 = value[2][3]; this.ColorMatrix.Matrix24 = value[2][4]; this.ColorMatrix.Matrix30 = value[3][0]; this.ColorMatrix.Matrix31 = value[3][1]; this.ColorMatrix.Matrix32 = value[3][2]; this.ColorMatrix.Matrix33 = value[3][3]; this.ColorMatrix.Matrix34 = value[3][4]; this.ColorMatrix.Matrix40 = value[4][0]; this.ColorMatrix.Matrix41 = value[4][1]; this.ColorMatrix.Matrix42 = value[4][2]; this.ColorMatrix.Matrix43 = value[4][3]; this.ColorMatrix.Matrix44 = value[4][4]; } } private ColorMatrix colorMatrix; public ColorMatrix ColorMatrix { get { return colorMatrix; } set { colorMatrix = value; } } private bool keepScale; public bool KeepScale { get { return keepScale; } set { keepScale = value; } } public override double ForegroundOpacity { get { return base.ForegroundOpacity; } set { double percent = value > 1 ? 1 : (value < 0 ? 0 : value); base.ForegroundOpacity = percent; this.ColorMatrix.Matrix33 = (float)percent; } } #endregion #region Constructor public ImageWatermarker(Image originImage, Image watermarkImage) : base(originImage) { this.WatermarkImage = watermarkImage; // Default values this.ColorMaps.Add(new ColorMap()); this.ColorMaps[0].OldColor = Color.FromArgb(255, 255, 255, 255); this.ColorMaps[0].NewColor = Color.FromArgb(0, 0, 0, 0); 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, 0.3f, 0.0f}, new float[]{0.0f, 0.0f, 0.0f, 0.0f, 1.0f} }; this.ColorMatrix = new ColorMatrix(colorMatrixElements); this.WatermarkSize = this.WatermarkImage.Size; this.KeepScale = true; } #endregion #region Methods protected override SizeF ComputeWatermarkSize() { return this.WatermarkSize; } protected override Image AddWatermarkToOriginImage() { this.WatermarkedImage = this.OriginImage; Graphics watermarkGraphic = Graphics.FromImage(this.WatermarkedImage); this.ImageAttributes.SetRemapTable(this.ColorMaps.ToArray(), ColorAdjustType.Bitmap); this.ImageAttributes.SetColorMatrix(this.ColorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap); watermarkGraphic.DrawImage(this.WatermarkImage, new Rectangle((int)this.X, (int)this.Y, (int)this.WatermarkSize.Width, (int)this.WatermarkSize.Height), 0, 0, this.WatermarkImage.Width, this.WatermarkImage.Height, GraphicsUnit.Pixel, this.ImageAttributes); watermarkGraphic.Dispose(); imageAttributes.Dispose(); return this.WatermarkedImage; } public void SetWatermarkWidth(int width) { float height = this.WatermarkSize.Height; if (this.KeepScale) { height = height * width / this.WatermarkSize.Width; } this.WatermarkSize = new SizeF(width, height); } public void SetWatermarkHeight(int height) { float width = this.WatermarkSize.Width; if (this.KeepScale) { width = width * height / this.WatermarkSize.Height; } this.WatermarkSize = new SizeF(width, height); } public void SetWatermarkSize(int width, int height) { this.WatermarkSize = new SizeF(width, height); this.KeepScale = false; } public override void Dispose() { base.Dispose(); this.WatermarkImage.Dispose(); } #endregion }}
using System; using System.Drawing; using System.Collections.Generic;namespace zizhujy.ImageHandler { public class TextWatermarker : Watermarker { #region Properties
private string watermarkText; public string WatermarkText { get { return watermarkText; } set { watermarkText = value; } } // 自动计算最合适的水印文本字体大小 private bool autoSize = true; public bool AutoSize { get { return autoSize; } set { autoSize = value; } } private double fontSizePercent; public double FontSizePercent { get { return fontSizePercent; } set { fontSizePercent = value > 1 ? 1 : (value <= 0.01 ? 0.01 : value); } } private List<Font> fonts = new List<Font>(); public List<Font> Fonts { get { return fonts; } set { fonts = value; } } private Font bestFont = new Font("Arial", 12, FontStyle.Regular, GraphicsUnit.Pixel); public Font BestFont{ get{ return bestFont; } set { bestFont = value; } } private StringFormat StringFormat { get { StringFormat format = new StringFormat(); if (this.ComputeX) { switch (this.HorizontalPosition) { case WatermarkHorizontalPostion.Left: format.Alignment = StringAlignment.Near; break; case WatermarkHorizontalPostion.Center: format.Alignment = StringAlignment.Center; break; case WatermarkHorizontalPostion.Right: format.Alignment = StringAlignment.Far; break; } } else { format.Alignment = StringAlignment.Near; } return format; } } #endregion #region Constructor public TextWatermarker(Image originImage, string watermarkText) : base(originImage) { this.WatermarkText = watermarkText; // Default values this.Fonts.Add(new Font("Arial", 18, FontStyle.Regular, GraphicsUnit.Pixel)); this.Fonts.Add(new Font("Arial", 16, FontStyle.Regular, GraphicsUnit.Pixel)); this.Fonts.Add(new Font("Arial", 14, FontStyle.Regular, GraphicsUnit.Pixel)); this.Fonts.Add(new Font("Arial", 12, FontStyle.Regular, GraphicsUnit.Pixel)); this.Fonts.Add(new Font("Arial", 10, FontStyle.Regular, GraphicsUnit.Pixel)); this.Fonts.Add(new Font("Arial", 8, FontStyle.Regular, GraphicsUnit.Pixel)); this.Fonts.Add(new Font("Arial", 6, FontStyle.Regular, GraphicsUnit.Pixel)); this.Fonts.Add(new Font("Arial", 4, FontStyle.Regular, GraphicsUnit.Pixel)); this.FontSizePercent = 30.00 / 480.00; this.AutoSize = true; } #endregion #region Methods public void ChangeFontFamily(string fontFamily) { FontFamily ff = new FontFamily(fontFamily); for (int i = 0; i < this.Fonts.Count; i++) { this.Fonts[i] = new Font(ff, this.Fonts[i].Size, this.Fonts[i].Style, this.Fonts[i].Unit, this.Fonts[i].GdiCharSet, this.Fonts[i].GdiVerticalFont); } this.BestFont = new Font(ff, this.BestFont.Size, this.BestFont.Style, this.BestFont.Unit, this.BestFont.GdiCharSet, this.BestFont.GdiVerticalFont); } protected override SizeF ComputeWatermarkSize() { FindAvailableMaxSizedFont(); return this.WatermarkSize; } protected override void UpdateXY() { if (this.ComputeX) { switch (this.HorizontalPosition) { case WatermarkHorizontalPostion.Left: this.X = this.HorizontalMarginPixel; break; case WatermarkHorizontalPostion.Center: this.X = this.OriginImage.Width / 2; break; case WatermarkHorizontalPostion.Right: this.X = (this.OriginImage.Width - this.HorizontalMarginPixel); break; default: break; } } if (this.ComputeY) { switch (this.VerticalPosition) { case WatermarkVerticalPostion.Top: this.Y = this.VerticalMarginPixel; break; case WatermarkVerticalPostion.Middle: this.Y = this.OriginImage.Height / 2 - this.WatermarkSize.Height / 2; break; case WatermarkVerticalPostion.Bottom: this.Y = (this.OriginImage.Height - this.VerticalMarginPixel - this.WatermarkSize.Height); break; default: break; } } } protected override Image AddWatermarkToOriginImage() { this.WatermarkedImage = this.OriginImage; Graphics g = Graphics.FromImage(this.WatermarkedImage); g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias; SolidBrush semiTransBrushShadow = new SolidBrush(this.ShadowColor); StringFormat format = this.StringFormat; g.DrawString(this.WatermarkText, this.BestFont, semiTransBrushShadow, new PointF(this.X + this.ShadowOffsetX, this.Y + this.ShadowOffsetY), format); SolidBrush semiTransBrush = new SolidBrush(this.ForeColor); g.DrawString(this.WatermarkText, this.BestFont, semiTransBrush, new PointF(this.X, this.Y), format); g.Dispose(); return this.WatermarkedImage; } private Font FindAvailableMaxSizedFont() { if (this.AutoSize) { this.BestFont = FindAvailableMaxSizedFont(false); if (this.BestFont.Size >= 16) { return this.BestFont; } else { return FindAvailableMaxSizedFont(true); } } else { return FindAvailableMaxSizedFont(true); } } private Font FindAvailableMaxSizedFont(bool byAbsoluteSizes) { if (byAbsoluteSizes) { this.Fonts.Sort(delegate(Font font1, Font font2) { return font2.Size.CompareTo(font1.Size); }); SizeF size = new SizeF(); Bitmap image = new Bitmap(1, 1); Graphics g = Graphics.FromImage(image); for (int i = 0; i < this.Fonts.Count; i++) { //size = MeasureSize(this.WatermarkText, this.Fonts[i]); size = g.MeasureString(this.WatermarkText, this.Fonts[i]); if ((ushort)(size.Width + this.HorizontalMarginPixel * 2) < (ushort)this.OriginImage.Width && (ushort)(size.Height + this.VerticalMarginPixel * 2) < (ushort)this.OriginImage.Height) { g.Dispose(); image.Dispose(); this.WatermarkSize = size; this.BestFont = this.fonts[i]; return this.Fonts[i]; } } g.Dispose(); image.Dispose(); this.WatermarkSize = new SizeF(0, 0); return null; } else { int fontSize = (int)(this.OriginImage.Height * this.FontSizePercent); fontSize = fontSize >= 1 ? fontSize : 1; this.BestFont = new Font(this.BestFont.FontFamily, fontSize, this.BestFont.Style, this.BestFont.Unit); this.WatermarkSize = MeasureSize(this.WatermarkText, this.BestFont); if ((ushort)(this.WatermarkSize.Width + this.HorizontalMarginPixel * 2) < (ushort)this.OriginImage.Width && (ushort)(this.WatermarkSize.Height + this.VerticalMarginPixel * 2) < (ushort)this.OriginImage.Height) { return this.BestFont; } else { this.WatermarkSize = new SizeF(0, 0); return null; } } } private SizeF MeasureSize(string text, Font font) { // Use a test image to measure the text. Bitmap image = new Bitmap(1, 1); Graphics g = Graphics.FromImage(image); SizeF size = g.MeasureString(text, font); g.Dispose(); image.Dispose(); return size; } #endregion }}
四、总结：
这里采用模板设计模式，可复用性高，能被引用在多种工程之中；可扩展性强，比如当有需要添加HTML水印时，只需要新建一个HtmlWatermarker类，并实现模板类Watermarker中的相关方法即可，不需要更改任何现有代码。
注意，模板设计模式很好地遵循了面向对象设计中的一个重要原则：对修改关闭，对扩展开放。
五、相关文件下载：
DLL 文件(若仅需使用)：ImageHandler.dll (18.00 kb)
整个项目文件(若还需开发)：ImageHandler.rar (45.03 kb)
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