我找到了一个很好的代码来缩小服务器上的图像大小，以避免不同浏览器的不良图像渲染。此代码适用于 MVC 应用程序。
我没有 C# 经验想知道我需要更改什么才能使此代码在 web 表单中工作。
<img src="@Url.Action("ResizeImage", "Controller", new { urlImage = "<url_image>", width = 35 })" />
public ActionResult ResizeImage(string imageUrl, int width)
{
WebImage wImage = new WebImage(imageUrl);
wImage = WebImageExtension.Resize(wImage, width);
return File(wImage.GetBytes(), "image/png");
}
public static class WebImageExtension
{
private static readonly IDictionary<string, ImageFormat> TransparencyFormats =
new Dictionary<string, ImageFormat>(StringComparer.OrdinalIgnoreCase) { { "png", ImageFormat.Png }, { "gif", ImageFormat.Gif } };
public static WebImage Resize(this WebImage image, int width)
{
double aspectRatio = (double)image.Width / image.Height;
var height = Convert.ToInt32(width / aspectRatio);
ImageFormat format;
if (!TransparencyFormats.TryGetValue(image.ImageFormat.ToLower(), out format))
{
return image.Resize(width, height);
}
using (Image resizedImage = new Bitmap(width, height))
{
using (var source = new Bitmap(new MemoryStream(image.GetBytes())))
{
using (Graphics g = Graphics.FromImage(resizedImage))
{
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
g.DrawImage(source, 0, 0, width, height);
}
}
using (var ms = new MemoryStream())
{
resizedImage.Save(ms, format);
return new WebImage(ms.ToArray());
}
}
}
}
更新：
我使用此代码调整图像大小
public static void ResizeImageFreeSize(string OriginalFile, string NewFile, int MinWidth, int MinHeight, string FileExtension)
{
var NewHeight = MinHeight;
var NewWidth = MinWidth;
// var OriginalImage = System.Drawing.Image.FromFile(OriginalFile); // THis statlement alon with generate error as file is locked so -->GDI+ keeps a lock on files from which an image was contructed. To avoid the lock, construct the image from a MemorySteam:
MemoryStream ms = new MemoryStream(File.ReadAllBytes(OriginalFile));
var OriginalImage = System.Drawing.Image.FromStream(ms);
if (OriginalImage.Width < MinWidth || OriginalImage.Height < MinHeight)
throw new Exception(String.Format("Invalid Image Dimensions, please upload an image with minmum dimensions of {0}x{1}px", MinWidth.ToString(), MinHeight.ToString()));
// If the image dimensions are the same then make the new dimensions the largest of the two mins.
if (OriginalImage.Height == OriginalImage.Width)
NewWidth = NewHeight = (MinWidth > MinHeight) ? MinWidth : MinHeight;
else
{
if (MinWidth > MinHeight)
NewHeight = (int)(OriginalImage.Height * ((float)MinWidth / (float)OriginalImage.Width));
else
NewWidth = (int)(OriginalImage.Width * ((float)MinHeight / (float)OriginalImage.Height));
}
// Just resample the Original Image into a new Bitmap
var ResizedBitmap = new System.Drawing.Bitmap(OriginalImage, NewWidth, NewHeight);
// Saves the new bitmap in the same format as it's source image
FileExtension = FileExtension.ToLower().Replace(".", "");
ImageFormat Format = null;
switch (FileExtension)
{
case "jpg":
Format = ImageFormat.Jpeg;
Encoder quality = Encoder.Quality;
var ratio = new EncoderParameter(quality, 100L);
var codecParams = new EncoderParameters(1);
codecParams.Param[0] = ratio;
// NewImage.Save(NewFile, GetEncoder(ImageFormat.Jpeg), codecParams);
ResizedBitmap.Save(NewFile, GetEncoder(ImageFormat.Jpeg), codecParams);
break;
case "gif":
Format = ImageFormat.Gif;
ResizedBitmap.Save(NewFile, Format);
break;
case "png":
Format = ImageFormat.Png;
ResizedBitmap.Save(NewFile, Format);
break;
default:
Format = ImageFormat.Png;
ResizedBitmap.Save(NewFile, Format);
break;
}
// ResizedBitmap.Save(NewFile, Format);
// Clear handle to original file so that we can overwrite it if necessary
OriginalImage.Dispose();
ResizedBitmap.Dispose();
}