Question

c#做图像查看器怎么实现图片放大缩小？请写代码

用c#做一个图片查看器，要怎样实现图片放大与缩小。。

Answer 1

//将图片变小
public static Bitmap CreateThumbnail(Bitmap source, int thumbWi, int thumbHi, bool maintainAspect)
{
// return the source image if it’s smaller than the designated thumbnail
if (source.Width < thumbWi && source.Height < thumbHi) return source;

Bitmap ret;
try
{
int wi = thumbWi;
int hi = thumbHi;

if (maintainAspect)
{
// maintain the aspect ratio despite the thumbnail size parameters
if (source.Width > source.Height)
{
wi = thumbWi;
hi = (int)(source.Height * ((decimal)thumbWi / source.Width));
}
else
{
hi = thumbHi;
wi = (int)(source.Width * ((decimal)thumbHi / source.Height));
}
}

// original code that creates lousy thumbnails
// System.Drawing.Image ret = source.GetThumbnailImage(wi,hi,null,IntPtr.Zero);
ret = new Bitmap(wi, hi);
using (Graphics g = Graphics.FromImage(ret))
{
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
g.FillRectangle(Brushes.White, 0, 0, wi, hi);
g.DrawImage(source, 0, 0, wi, hi);
}
}
catch
{
ret = null;
}

return ret;
}