Resizing image proportionally in ASP.NET C# by specifying either Height or Width

问题

I need a code that will allow me to resize images, but with the following functionality:

1) resize image upon upload

2) Resize image proportionally by specifying either height or width.

Note:

Should be done in ASP.NET C#

For example: The function should get the a width OR a height, and resize the image proportionally for the give height OR Width. Let's say that the image is 400(w)x100(h). I want to tell the function to resize the image to a specific height, let's say 80px. The function should resize the image proportionally while setting the image height to 80px and the width accordingly. Another option is ti tell the function the width, let's say 200px, and the function should resize the image to 200px width and set the height accordingly.

3) save the image to a specific location (path).

4) Function can work with uploaded image or by specifying an image path.

5) I want to be able to choose the image quality

6) Only need this for JPEG

Can somebody please help me out with this. Thanks.

回答1:

Although it seems like you should be able to copy and paste a snippet to do this, there are a ton of pitfalls you need to look out for if you're building your own image resizing system. It's better to use a proven, tested, and supported open-source library.

To resize to a file directly from HttpPostedFile, call

ImageBuilder.Current.Build(httpPostedFile, "img.jpg", new ResizeSettings("width=200&quality=90"));

To resize an existing file, call

ImageBuilder.Current.Build("orig.jpg", "img.jpg", new ResizeSettings("width=200&quality=90"));

The ImageResizing.Net library is free, and MIT-licensed (no worries about licensing problems).

回答2:

Last day I found imageresizer and its great. and good API. Works Great. Downloaded from Visual studio 2010 Extension Manager: http://nuget.org/.

Easy Steps to download API in VS-2010:

1). Install Extension http://nuget.org/.

3). Find and Install ImageResizing

4).Then Code: (I m using here cropping. you can use any) Documentation on imageresizing.net

string uploadFolder = Server.MapPath(Request.ApplicationPath + "images/");
FileUpload1.SaveAs(uploadFolder + FileUpload1.FileName);


//The resizing settings can specify any of 30 commands.. See http://imageresizing.net for details.
ResizeSettings resizeCropSettings = new ResizeSettings("width=200&height=200&format=jpg&crop=auto");

//Generate a filename (GUIDs are safest).
string fileName = Path.Combine(uploadFolder, System.Guid.NewGuid().ToString());

//Let the image builder add the correct extension based on the output file type (which may differ).
fileName = ImageBuilder.Current.Build(uploadFolder + FileUpload1.FileName, fileName, resizeCropSettings, false, true);

Try!!! its very awsumm and easy to use. thanks.

回答3:

Taken from this Stackoverflow answer, I come up with:

public static Image Resize(this Image image, int maxWidth = 0, int maxHeight = 0)
    {
        if (maxWidth == 0)
            maxWidth = image.Width;
        if (maxHeight == 0)
            maxHeight = image.Height;

        var ratioX = (double)maxWidth / image.Width;
        var ratioY = (double)maxHeight / image.Height;
        var ratio = Math.Min(ratioX, ratioY);

        var newWidth = (int)(image.Width * ratio);
        var newHeight = (int)(image.Height * ratio);

        var newImage = new Bitmap(newWidth, newHeight);
        Graphics.FromImage(newImage).DrawImage(image, 0, 0, newWidth, newHeight);
        return newImage;
    }

To resize Image specifying its maxWidth:

var _image = Image.FromStream(Source);
var _thumbImage = _image.Resize(100);

To resize Image specifying its maxHeight:

var _image = Image.FromStream(Source);
var _thumbImage = _image.Resize(maxHeight: 100);

回答4:

Code I use for image resizing: http://sietch.net/ViewNewsItem.aspx?NewsItemID=105

回答5:

This is how is did in my project

On Button click while uploading file:

System.Drawing.Bitmap bmpPostedImage = new System.Drawing.Bitmap(File1.PostedFile.InputStream);
     System.Drawing.Image objImage = ScaleImage(bmpPostedImage, 81);
     objImage.Save(SaveLocation,ImageFormat.Png);
     lblmsg.Text = "The file has been uploaded.";

public static System.Drawing.Image ScaleImage(System.Drawing.Image image, int maxHeight)
        {
            var ratio = (double)maxHeight / image.Height;

            var newWidth = (int)(image.Width * ratio);
            var newHeight = (int)(image.Height * ratio);

            var newImage = new Bitmap(newWidth, newHeight);
            using (var g = Graphics.FromImage(newImage))
            {
                g.DrawImage(image, 0, 0, newWidth, newHeight);
            }
            return newImage;
        }

More Detail Click here

https://codepedia.info/how-to-resize-image-while-uploading-in-asp-net-using-c/

来源：https://stackoverflow.com/questions/6848497/resizing-image-proportionally-in-asp-net-c-sharp-by-specifying-either-height-or

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ASP.NET

image

resize

imageresizer