从 URL 图像动态生成缩略图

发布于 2024-12-13 15:19:13 字数 156 浏览 0 评论 0原文

我想知道是否有人有一些代码/有用的链接解释我如何做到这一点。我很可能会这样使用它：

<img src="ShowThumb.aspx?image=http://the_image.jpg" alt="" />

谢谢。

原文

I was wondering if anyone has some code/useful link explaining on how I could do this.
I would most likely use it this way:

<img src="ShowThumb.aspx?image=http://the_image.jpg" alt="" />

Thanks.

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手长情犹 2024-12-20 15:19:13

使用通用处理程序文件 (.ashx)，而不是使用 .aspx 文件。这意味着您只需要 1 个文件（无标记文件），因此它更整洁、更快。毕竟，您没有生成 Web 表单，因此 .aspx 文件不是您想要的。

您可以使用 System.Drawing.Graphics.DrawImage() 生成缩略图。

像这样简单的事情就可以工作：

Bitmap bmpOut = new Bitmap(width, height);
Bitmap B = new Bitmap(context.Server.MapPath(ImageURL));

Graphics g = Graphics.FromImage(bmpOut);
g.InterpolationMode = InterpolationMode.High;
g.DrawImage(B, 0, 0, width, height);


context.Response.ContentType = "image/PNG";
MemoryStream MemStream = new MemoryStream();
B.Save(MemStream, System.Drawing.Imaging.ImageFormat.Png);

B.Dispose();

MemStream.WriteTo(HttpContext.Current.Response.OutputStream);

Where width & height 是 integer 值，ImageURL 是本地 URI 字符串

我不会使用 HTML/CSS 中的宽度/高度属性来调整图像大小。这意味着您将全尺寸图像发送到客户端，浪费了每个人的带宽和时间！此外，当 HTML 调整它的大小时，它通常会做一些粗制滥造的扭曲工作。

顺便说一句，我曾经像这样生成动态缩略图，但我认为，当每次发出 HTTP 请求时都要调整图像大小时，性能会受到影响。

因此，每当上传主图像时，我都会将缩略图保存到物理位置，并在 HTML 中调用它。

Rather than using an .aspx file, use a Generic Handler file (.ashx). This means you only require the 1 file (no markup file), so its a bit neater and a bit quicker. Afterall, you're not generating a web form, so an .aspx file isn't what you're after.

You can make use of System.Drawing.Graphics.DrawImage() to produce a thumbnail.

Something as simple as this will work:

Bitmap bmpOut = new Bitmap(width, height);
Bitmap B = new Bitmap(context.Server.MapPath(ImageURL));

Graphics g = Graphics.FromImage(bmpOut);
g.InterpolationMode = InterpolationMode.High;
g.DrawImage(B, 0, 0, width, height);


context.Response.ContentType = "image/PNG";
MemoryStream MemStream = new MemoryStream();
B.Save(MemStream, System.Drawing.Imaging.ImageFormat.Png);

B.Dispose();

MemStream.WriteTo(HttpContext.Current.Response.OutputStream);

Where width & height are integer values, and ImageURL is a local URI string

I wouldn't resize your image using width/height attributes in HTML/CSS. This means you are sending the full size image to the client wasting everyones bandwidth and time! Furthermore, when HTML resizes it, it usually does a shoddy distorted job of it.

On a side note, I used to generate on-the-fly thumbnails like this, but decided that the performance was compromised as you are resizing the image everytime a HTTP request is made.

Therefore, whenever the main image was uploaded, I saved the thumbnail to a physical location, and called that in my HTML.

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