How to check if a jpeg image file is actually a valid image before trying to load?

Question

In C#.NET 4.0, based on a problem I had with downloading false images (saving an error aspx page as image.jpg instead of an actual image in image.jpg), I need to somehow read the file and identify if it is a valid image or not. I just need 1 function public bool IsValidJpgImage(string ImageFilename); Anything that returns false (is not a valid image file) I will delete from the disk.

You can begin by check the file extension, then go on reading and validating the jpeg header. — Cyclonecode, Nov 19 '11 at 23:19
Check out: http://stackoverflow.com/questions/210650/validate-image-from-file-in-c-sharp. — Gibron, Nov 19 '11 at 23:21
You need to add to your question that you have over 7000 images to search through. — Andrew Barber, Nov 19 '11 at 23:49

score 6 · Accepted Answer · edited Nov 16 '12 at 14:32

6

As far I as I know all JPEGs begin internally with same 10 character ASCII string although I can't remember what the first 6 characters are. This is quick/dirty method of indentifying a jpeg image even if the file extension is wrong.

grep -P '^......JFIF' ./'raccoon paint.jpeg'

If the image is not a jpeg the match will fail.

edited Nov 16 '12 at 14:32

Sirko

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answered Nov 16 '12 at 14:12

Santana

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score 1 · Answer 2 · answered Feb 15 '12 at 06:13

This code is for taking less then 500kb size and .jpg format before upload image

protected void btnOk_Click(object sender, EventArgs e)
{
    long maxsize = 512000;
    string str = Path.GetFileName(FileUpload1.FileName);
    int filesize = FileUpload1.PostedFile.ContentLength;
    string fileexe = Path.GetExtension(FileUpload1.FileName);
    if (filesize <= maxsize )
    {
        if (fileexe == ".jpg" || fileexe == ".jpeg")
        {
            FileUpload1.SaveAs(Server.MapPath("~/Image/" + str));
        }
        else
        {
            lblMsg.Text = "Image extension must be jpg or jpeg";
        }
    }
    else
    {
        lblMsg.Text = "File size is too large.";
    }

}

How to check if a jpeg image file is actually a valid image before trying to load?

2 Answers2

This code is for taking less then 500kb size and .jpg format before upload image

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