一些图片处理函数收集

切割图片:

public Image CutImage(Image img, Rectangle rect)

{

Image destImg = new Bitmap(rect.Width,rect.Height);

Graphics g = Graphics.FromImage(destImg);

Rectangle destRect=new Rectangle(0,0,rect.Width,rect.Height);

g.DrawImage(img, destRect, rect, GraphicsUnit.Pixel);

return destImg;

}

使用Graphics.DrawImgage方法, 这个方法是把源图片指定的位置绘制到目标区域上.

注意:当源图片区域跟目标区域长宽比不等时图片将被拉缩,等比例不等值时可以实现缩略图,等值(长和宽)时就是切割了.

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半透明水印:

参考资料:给图片加透明度水印的方法（c#）

像素拷贝用Marchal.Copy,注意字节跌加时的偏移量

需要导入的命名空间

srcImg是底图,destImg是logo

using System.Drawing.Imaging;

using System.Drawing.Drawing2D;

using System.Runtime.InteropServices;

public Image WaterMark(Bitmap srcImg, Bitmap destImg, double opacity)

{

int ypos = (int)((srcImg.Height * .99) - destImg.Height);

int xpos = (int)((srcImg.Width * .99) - destImg.Width);

BitmapData srcBD = srcImg.LockBits(new Rectangle(0,0,srcImg.Width,srcImg.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);

BitmapData destBD = destImg.LockBits(new Rectangle(0, 0, destImg.Width, destImg.Height), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);

IntPtr srcPtr = srcBD.Scan0;

IntPtr destPtr = destBD.Scan0;

int srcLength = srcBD.Stride * srcBD.Height;

int destLength = destBD.Stride * destBD.Height;

byte[] srcBytes = new byte[srcLength];

byte[] destBytes = new byte[destLength];

Marshal.Copy(srcPtr, srcBytes, 0, srcLength);

Marshal.Copy(destPtr, destBytes, 0, destLength);

for (int y = 0; y < destBD.Height; y++)

{

for (int x = 0; x < destBD.Stride; x++)

{

srcBytes[(ypos + y) * (srcBD.Stride) + xpos * 3 + x] = (byte)(srcBytes[(ypos + y) * (srcBD.Stride) + xpos * 3 + x] * (1 - opacity) + destBytes[y * (destBD.Stride) + x] * opacity);

}

}

Marshal.Copy(srcBytes, 0, srcPtr, srcLength);

destImg.UnlockBits(destBD);

srcImg.UnlockBits(srcBD);

return srcImg;

}

文字透明水印:

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public Image WaterMark(Bitmap srcImg, string text, double opacity)

{

//寻找合适的字体大小

Graphics g = Graphics.FromImage(srcImg);

int[] fontSizes =new int[] {24,22,20,18,16,14,12,10,8,6,4};

Font font=null;

SizeF size=new SizeF();

for (int i = 0; i < fontSizes.Length; i++)

{

//字体，以及字体样式（加粗，斜体，下划线等)

font = new Font("Arial", fontSizes[i], FontStyle.Bold);

size = g.MeasureString(text, font);

if ((ushort)size.Width < (ushort)srcImg.Width) break;

}

g.Dispose();

//右下方

int ypos =(int)((srcImg.Height * .99) - (int) size.Height);

int xpos =(int)((srcImg.Width * .99) - (int)size.Width );

Bitmap bmp = new Bitmap((int)size.Width,(int) size.Height);

Graphics pic = Graphics.FromImage(bmp);

pic.SmoothingMode=SmoothingMode.AntiAlias;

pic.DrawImage(srcImg, new Rectangle(0, 0,bmp.Width,bmp.Height), new Rectangle(xpos, ypos,bmp.Width,bmp.Height), GraphicsUnit.Pixel);

Brush brush=new SolidBrush(Color.WhiteSmoke);

pic.DrawString(text, font, brush, 0, 0);

brush.Dispose();

//透明度处理

Rectangle srcRect=new Rectangle(0,0,srcImg.Width,srcImg.Height);

BitmapData srcBD = srcImg.LockBits(srcRect, ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);

BitmapData destBD = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadOnly,PixelFormat.Format24bppRgb);

IntPtr srcPtr = srcBD.Scan0;

IntPtr destPtr = destBD.Scan0;

int srcLength = srcBD.Stride * srcBD.Height ;

int destLength =destBD.Stride * destBD.Height ;

byte[] srcBytes = new byte[srcLength];

byte[] destBytes = new byte[destLength];

Marshal.Copy(srcPtr, srcBytes, 0, srcLength);

Marshal.Copy(destPtr, destBytes, 0, destLength);

for (int y = 0; y < destBD.Height; y++)

{

for (int x = 0; x <destBD.Stride ; x++)

{

srcBytes[(ypos + y) * (srcBD.Stride) +xpos * 3 + x] = (byte)(srcBytes[(ypos + y) * (srcBD.Stride) + xpos * 3 + x] * (1 - opacity) + destBytes[y * (destBD.Stride) + x ] * opacity);

}

}

Marshal.Copy(srcBytes, 0, srcPtr,srcLength);

bmp.UnlockBits(destBD);

srcImg.UnlockBits(srcBD);

return srcImg;

}

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图片等比例缩略图:

说明,先将图片剪切,再等比例缩小,这样图片不变形,另外小图片质量比GetThumbnailImage方法要清晰点,

public static bool Thum(string srcPath, string destPath, double width, double height)

{

System.Drawing.Image img = new Bitmap(srcPath);

//生成图片大小必需小于原图

if (img.Width < width)

{

width = img.Width;

}

if (img.Height < height)

{

height = img.Height;

}

//删除的高度，与宽度

double cutWidth, cutHeight;

cutWidth = (img.Width * height / img.Height - width); //宽度切割,高度缩放

cutHeight = (img.Height * width / img.Width - height);//高度切割,宽度缩放

byte flag = 0;//0 截高，1 截宽

//这里的截宽是指缩略图的宽将被截，不是指原图，

//1. 按原图比例，选择缩略图的高固定，计算出来的宽如果大于指定的宽，那么就按高固定，计算出来的宽来生成缩略图，再按给定大小截取

//2. 按原图比例，选择缩略图的宽固定，计算出来的高如果大于指定的高，那么就按宽固定，计算出来的高来生成缩略图，再按给定大小截取

//3. 因为长宽比只能取{1,>1,<1}三种情况

flag = (byte)(cutHeight <= cutWidth ? 0 : 1);

//System.Drawing.Image.GetThumbnailImageAbort myCallback=new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback);

System.Drawing.Image thumImg;

if (flag == 0)

thumImg = new Bitmap(img, (int)width, (int)height + (int)cutHeight); //img.GetThumbnailImage((int)width, (int)height + (int)cutHeight, myCallback, IntPtr.Zero);

else

thumImg = new Bitmap(img, (int)width + (int)cutWidth, (int)height);// img.GetThumbnailImage((int)width + (int)cutWidth, (int)height, myCallback, IntPtr.Zero);

System.Drawing.Bitmap destImg = new Bitmap((int)width, (int)height);

Graphics g = Graphics.FromImage(destImg);

Rectangle rect = new Rectangle(0, 0, (int)width, (int)height);

//填充透明背景

g.FillRectangle(Brushes.White,rect);

g.DrawImage(thumImg, rect, rect, GraphicsUnit.Pixel);

g.Save();

destImg.Save(destPath, GetFormat(destPath));

thumImg.Dispose();

img.Dispose();

destImg.Dispose();

return true;

}