如何将按比例生成的缩略图用白色背景填充丢失的部分?
如宽高是100PX时,有时候可能高度不足100,如何用白色背景补上不足部分?
以下是原来的代码:public bool GetThumbNail( FileUpload file, string savePath, int width, int height, string mode )
{ //缩略图
System.Drawing.Image originalImage = System.Drawing.Image.FromStream(file.PostedFile.InputStream);
file.Dispose();
int towidth = width;
int toheight = height; int x = 0;
int y = 0;
int ow = originalImage.Width;
int oh = originalImage.Height; switch ( mode )
{
case "HW"://指定高宽缩放(可能变形)
break;
case "W"://指定宽,高按比例
toheight = originalImage.Height * width / originalImage.Width;
break;
case "H"://指定高,宽按比例
towidth = originalImage.Width * height / originalImage.Height;
break;
case "Cut"://指定高宽裁减(不变形)
if ( (double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight )
{
oh = originalImage.Height;
ow = originalImage.Height * towidth / toheight;
y = 0;
x = ( originalImage.Width - ow ) / 2;
}
else
{
ow = originalImage.Width;
oh = originalImage.Width * height / towidth;
x = 0;
y = ( originalImage.Height - oh ) / 2;
}
break;
default:
break;
} //新建一个bmp图片
System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight); //新建一个画板
Graphics g = System.Drawing.Graphics.FromImage(bitmap); //设置高质量插值法
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; //设置高质量,低速度呈现平滑程度
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; //清空画布并以透明背景色填充
g.Clear(Color.Transparent); //在指定位置并且按指定大小绘制原图片的指定部分
g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),
new Rectangle(x, y, ow, oh),
GraphicsUnit.Pixel); try
{
//以jpg格式保存缩略图
bitmap.Save(savePath, System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch
{
return false;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
} return true;
}
如宽高是100PX时,有时候可能高度不足100,如何用白色背景补上不足部分?
以下是原来的代码:public bool GetThumbNail( FileUpload file, string savePath, int width, int height, string mode )
{ //缩略图
System.Drawing.Image originalImage = System.Drawing.Image.FromStream(file.PostedFile.InputStream);
file.Dispose();
int towidth = width;
int toheight = height; int x = 0;
int y = 0;
int ow = originalImage.Width;
int oh = originalImage.Height; switch ( mode )
{
case "HW"://指定高宽缩放(可能变形)
break;
case "W"://指定宽,高按比例
toheight = originalImage.Height * width / originalImage.Width;
break;
case "H"://指定高,宽按比例
towidth = originalImage.Width * height / originalImage.Height;
break;
case "Cut"://指定高宽裁减(不变形)
if ( (double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight )
{
oh = originalImage.Height;
ow = originalImage.Height * towidth / toheight;
y = 0;
x = ( originalImage.Width - ow ) / 2;
}
else
{
ow = originalImage.Width;
oh = originalImage.Width * height / towidth;
x = 0;
y = ( originalImage.Height - oh ) / 2;
}
break;
default:
break;
} //新建一个bmp图片
System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight); //新建一个画板
Graphics g = System.Drawing.Graphics.FromImage(bitmap); //设置高质量插值法
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; //设置高质量,低速度呈现平滑程度
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; //清空画布并以透明背景色填充
g.Clear(Color.Transparent); //在指定位置并且按指定大小绘制原图片的指定部分
g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),
new Rectangle(x, y, ow, oh),
GraphicsUnit.Pixel); try
{
//以jpg格式保存缩略图
bitmap.Save(savePath, System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch
{
return false;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
} return true;
}
g.Clear(Color.White);
Bitmap whiteBitmap = new Bitmap(100,100);
Graphics g = Graphics.FromImage(whiteBitmap)
g.DrawImage(whiteBitmap,new Rectangle(0,0,100,100));
画了背景层以后再画缩略图了。
g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight);
试试看
不过我不建议你填充白色,这样如果哪天你的页面的背景色想改成其他颜色,这是白色会很难看,还是透明的好,如果你需要白色边,那可以用CSS来实现。
先用白色填充背景,之后在上面生成缩略图也就基于白色背景了。
System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
改成
//新建一个bmp图片
System.Drawing.Image bitmap = new System.Drawing.Bitmap(ow, oh);