/// <summary>
/// 根据指定的宽高，等比缩放图片，多余的部分会以白边补全
/// </summary>
/// <param name="source"></param>
/// <param name="width"></param>
/// <param name="height"></param>
/// <param name="quality">质量，这个参数并不太会影响图像的呈现质量，主要是可以提高速度,质量越低速度越快</param>
/// <param name="background"></param>
/// <returns></returns>
public static Bitmap Scale(this Image source, int width, int height, ImageQuality quality, Color background)
{
var rawRect = new DynamicRectangle()
{
X = 0,
Y = 0,
Width = source.Width,
Height = source.Height
};
var targetRect = rawRect.Scale(width, height, true);
Bitmap target = null;
try
{
target = new Bitmap(width, height);
using (var gh = Graphics.FromImage(target))
{
gh.CompositingQuality = quality.Compositing;
gh.SmoothingMode = quality.Smoothing;
gh.InterpolationMode = quality.Interpolation;
gh.PixelOffsetMode = quality.PixelOffset;
//gh.FillRectangle(new SolidBrush(background), 0, 0, width, height);
//清空画布并以指定的背景色填充
gh.Clear(background);
Rectangle destrect = targetRect.ToRectangle();
gh.DrawImage(source, destrect, 0, 0, source.Width,
source.Height, GraphicsUnit.Pixel);
}
}
catch (Exception ex)
{
if (target != null)
{
target.Dispose();
}
throw ex;
}
return(target);
}
/// <summary>
/// 将原始长宽缩放到指定的大小
/// 这时得到的是图像在指定区域中实际的偏移量和大小
/// </summary>
/// <param name="targetWidth"></param>
/// <param name="targetHeight"></param>
/// <param name="isEnlarge">当源图片小于需要展现的区域大小时，是否需要将源图片放大</param>
/// <returns></returns>
public DynamicRectangle Scale(int targetWidth, int targetHeight, bool isEnlarge = false)
{
if (targetWidth < 0 || targetHeight < 0)
{
throw new DrawingException("DynamicRectangle 参数异常");
}
if (targetWidth == 0 && targetHeight == 0)
{
return(this);
}
DynamicRectangle result = new DynamicRectangle();
result.X = 0;
result.Y = 0;
//先等比缩放
if (this.Width > this.Height)
{
//宽大于高，以宽等比缩放
if (isEnlarge)
{
result.Width = targetWidth;
result.Height = (int)(this.Height * (double)result.Width / (double)this.Width);
if (result.Height > targetHeight)//得到的结果比需要的高度高，则根据高度缩放
{
result.Height = targetHeight;
result.Width = (int)(this.Width * (double)result.Height / (double)this.Height);
}
}
else
{
result.Width = this.Width > targetWidth ? targetWidth : this.Width;
result.Height = (int)(this.Height * (double)result.Width / (double)this.Width);
if (result.Height > targetHeight)//得到的结果比需要的高度高，则根据高度缩放
{
result.Height = this.Height > targetHeight ? targetHeight : this.Height;
result.Width = (int)(this.Width * (double)result.Height / (double)this.Height);
}
}
}
else
{
//高大于宽，以高等比缩放
if (isEnlarge)
{
result.Height = targetHeight;
result.Width = (int)(this.Width * (double)result.Height / (double)this.Height);
if (result.Width > targetWidth)//得到的结果比需要的宽度宽，则根据宽度缩放
{
result.Width = targetWidth;
result.Height = (int)(this.Height * (double)result.Width / (double)this.Width);
}
}
else
{
result.Height = this.Height > targetHeight ? targetHeight : this.Height;
result.Width = (int)(this.Width * (double)result.Height / (double)this.Height);
if (result.Width > targetWidth)//得到的结果比需要的宽度宽，则根据宽度缩放
{
result.Width = this.Width > targetWidth ? targetWidth : this.Width;
result.Height = (int)(this.Height * (double)result.Width / (double)this.Width);
}
}
}
if (result.Width < targetWidth)
{
result.X = (targetWidth - result.Width) / 2;
}
if (result.Height < targetHeight)
{
result.Y = (targetHeight - result.Height) / 2;
}
return(result);
}