/// <summary>
/// 制作缩略图
/// </summary>
/// <param name="fileName">原图路径</param>
/// <param name="newFileName">新图路径</param>
/// <param name="maxWidth">最大宽度</param>
/// <param name="maxHeight">最大高度</param>
public static void MakeThumbnailImage(string fileName, string newFileName, int maxWidth, int maxHeight)
{
Image original = Image.FromFile(fileName);
Size _newSize = ResizeImage(original.Width, original.Height, maxWidth, maxHeight);
Image displayImage = new Bitmap(original, _newSize);
try
{
displayImage.Save(newFileName, GetFormat(fileName));
}
finally
{
original.Dispose();
}
}
/// <summary>
/// 计算新尺寸
/// </summary>
/// <param name="width">原始宽度</param>
/// <param name="height">原始高度</param>
/// <param name="maxWidth">最大新宽度</param>
/// <param name="maxHeight">最大新高度</param>
/// <returns></returns>
private static Size ResizeImage(int width, int height, int maxWidth, int maxHeight)
{
decimal MAX_WIDTH = (decimal)maxWidth;
decimal MAX_HEIGHT = (decimal)maxHeight;
decimal ASPECT_RATIO = MAX_WIDTH / MAX_HEIGHT;
int newWidth, newHeight;
decimal originalWidth = (decimal)width;
decimal originalHeight = (decimal)height;
if (originalWidth > MAX_WIDTH || originalHeight > MAX_HEIGHT)
{
decimal factor;
// determine the largest factor
if (originalWidth / originalHeight > ASPECT_RATIO)
{
factor = originalWidth / MAX_WIDTH;
newWidth = Convert.ToInt32(originalWidth / factor);
newHeight = Convert.ToInt32(originalHeight / factor);
}
else
{
factor = originalHeight / MAX_HEIGHT;
newWidth = Convert.ToInt32(originalWidth / factor);
newHeight = Convert.ToInt32(originalHeight / factor);
}
}
else
{
newWidth = width;
newHeight = height;
}
return new Size(newWidth, newHeight);
}