C #: Show Thumbnail without resizing image in ASP

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C #: Show Thumbnail without resizing image in ASP

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#1 by (2 votes)

2

I do not want to let decrease images by setting width and height in asp.

Example:

<asp:Image Width="70" Height="90"
 ID="Image1" runat="server" ImageUrl=' <%# @"\imgpe\" + Eval("CODFOTO") + @".jpg" %>'/>

I would like to resize the file and reference the direct size.

Example: I have an image that I use in a page, URL: /imgpe/2222222.jpg with Dimensions 267 x 400

I would like to show a thumbnail of this image on another page with dimensions 70 x 90.

Without creating a new file.

Creating memory only temporarily and making the site page faster by having lighter images.

I've seen several Plugins that do this, but for security I do not use them.

How do I do this in C #?

c# asp.net

asked by anonymous 08.05.2015 / 20:23

1 answer

Load dynamic data into javascript Problems with SELECT option with PDO

score 2 · Accepted Answer

What you want is a backend service that is responsible for resizing images without storing them. Here are some snippets of code that can help you:

Create a page where you get the parameters Url , width and height .

Validate content received:

string url = Request["Url"];
int? width = Request["width"];
int? height = Request["height"];

Uri uriResult;
var isUrl = Uri.TryCreate(url, UriKind.Absolute, out uriResult) &&
                uriResult.Scheme == Uri.UriSchemeHttp;

If the URL is valid, download the content, and create an Image object:

var httpWebRequest = (HttpWebRequest)WebRequest.Create(url);
using (var httpWebReponse = (HttpWebResponse)httpWebRequest.GetResponse())
{
    using (var stream = httpWebReponse.GetResponseStream())
    {
        Image image = Image.FromStream(stream);
    }
}

Validate the reported dimensions. If one of the parameters is missing, use the corresponding dimension of the original image:
```
if (width == null)
    width = image.Width;

if (height == null)
    height = image.Height;
```
Resize the image to the desired size (the ResizeImage function is at the end of this post):
```
image = ResizeImage(image, (int)width, (int)height);
```

Send resized content to the client:

using(MemoryStream ms = new MemoryStream())
{
     image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
     ms.WriteTo(context.Response.OutputStream);
}

Next, the image resizing function. It performs the equivalent of the CSS rule background-size: contain :

public static Image ResizeImage(Image image, int width, int height)
{
    var destRatio = ((float) width/height);
    var srcRatio = ((float) image.Width/image.Height);
    int intermediateWidth;
    int intermediateHeight;
    var widthOffSet = 0;
    var heightOffSet = 0;

    if (srcRatio <= destRatio)
    {
        intermediateWidth = width;
        intermediateHeight = (int) (intermediateWidth/srcRatio);
        heightOffSet = 0;
    }
    else
    {
        intermediateHeight = height;
        intermediateWidth = (int) (intermediateHeight*srcRatio);
        widthOffSet = (intermediateWidth - width)/2;
    }

    var bmPhoto = new Bitmap(intermediateWidth, intermediateHeight, PixelFormat.Format24bppRgb);

    Graphics.FromImage(bmPhoto).DrawImage(image, 0, 0, intermediateWidth, intermediateHeight);

    var outputImage = new Bitmap(width, height);
    var section = new Rectangle(new Point(widthOffSet, heightOffSet), new Size(width, height));

    var preoutputGrp = Graphics.FromImage(outputImage);
    preoutputGrp.InterpolationMode = InterpolationMode.HighQualityBicubic;
    preoutputGrp.DrawImage(bmPhoto, 0, 0, section, GraphicsUnit.Pixel);
    preoutputGrp.Dispose();
    bmPhoto.Dispose();

    return outputImage;
}

Here are the results of my test implementation:

Original Image: link

Page call:

link

64x64 version:

Version64x128:

32x32 Version: