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;
}