如何生成这样的缩略图

Question

缩略图

Answer 1

伪代码：double 高宽比 = 3.0 / 4.0;
if (图片原始的宽 / 高宽比 > 原始图片的高)
{
    // 图片过扁，那么用图片的高，并且切掉左右多余的部分
    Rect r;
    r.Left = (图片原始的宽 - 图片原始的高 * 高宽比) / 2
    r.Top = 0
    r.Width =  图片原始的高 * 高宽比
    r.Height = 原始图片的高
    将这个区域的图片缩放
}
else
{
    // 图片过瘦，那么用图片的宽，并且切掉上下多于的部分
    ...
}

Answer 2

用Bitmap.Clone(x,y,width,height)就可以

Answer 3

 Refer:
http://www.cnblogs.com/insus/p/3627437.html

Answer 4

 protected virtual  Size CalculateDimensions(Size originalSize, int targetSize)
        {
            var newSize = new Size();
            if (originalSize.Height > originalSize.Width) // portrait 
            {
                newSize.Width = (int)(originalSize.Width * (float)(targetSize / (float)originalSize.Height));
                newSize.Height = targetSize;
            }
            else // landscape or square
            {
                newSize.Height = (int)(originalSize.Height * (float)(targetSize / (float)originalSize.Width));
                newSize.Width = targetSize;
            }
            return newSize;
        }public void NewPicture(byte[] PictureBinary, int offsetX = 0, int offsetY = 0, int targetSize = 0, double matrix = 1)
        {
            var picStream = new MemoryStream(PictureBinary);
            var picBit = new Bitmap(picStream);
            var newSize = CalculateDimensions(picBit.Size, targetSize);
            if (newSize.Width < 1)
                newSize.Width = 1;
            if (newSize.Height < 1)
                newSize.Height = 1;
            var newBitMap = new Bitmap(200, 200);//the new picture size
            var g = Graphics.FromImage(newBitMap);
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
            g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
            g.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;            g.DrawImage(picBit, offsetX, offsetY, newSize.Width, newSize.Height);
string localFilename = string.Format("{0}_{1}.{2}", picture.Id.ToString("10000000"), "combine", lastPart); 
            var ici = GetImageCodecInfoFromExtension(lastPart) ?? GetImageCodecInfoFromMimeType("image/jpeg");
    var ep = new EncoderParameters();
            ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, this.ImageQuality);
            newBitMap.Save(Path.Combine(this.LocalThumbImagePath, localFilename), ici, ep);
            newBitMap.Dispose();
            picBit.Dispose();
}