Why does Image.FromFile return System.Drawing.Bitmap?

Question

I'm new to using c# with asp.net ajax so any help is appreciated. I am using System.Drawing.Image to get my image's virtual path with Image.FromFile() and want to return the image to be set up in my web application. Thanks in advance for any response!

I have created a physical path then converted it to a virtual path then used Server.MapPath to get the equivalent path to assign to my Image image.

string pImagePath = @"C:\Apps\WebApp.Roll\Images\Profiles\" + item.Value.ToString();
string vImagePath = pImagePath.Replace(@"C:\Apps\WebApp.Roll", "~").Replace(@"\", "/");
Image image = Image.FromFile(System.Web.HttpContext.Current.Server.MapPath(vImagePath), true);

#item.value is name of the image file.

My path is correct but whenever I debug to see what my Image image is, it tells me that my image is System.Drawing.BitMap What am I doing wrong?

I'm confused. If you didn't expect the `Image.FromFile()` method to return a memory-loaded bitmap, what did you expect? — gunr2171, Jun 10 '19 at 15:52
My image is a jpg, do I need to use a converter? Or should I be using Graphics.DrawImage because right now when I load my WebApplication I get back System.Drawing.BitMap. — Rae, Jun 10 '19 at 15:52
Possible duplicate of [C# read a JPEG from file and store as an Image](https://stackoverflow.com/questions/330346/c-sharp-read-a-jpeg-from-file-and-store-as-an-image) — gunr2171, Jun 10 '19 at 15:54
It's not clear at all from the question what the problem is here. Are you unable to return the `Image`? What error are you getting? Or perhaps you're confusing the `System.Drawing.Bitmap` class with the `BMP` file extension? They are two different things, you know. Please read [this](https://learn.microsoft.com/en-us/dotnet/api/system.drawing.bitmap?view=netframework-4.8) for more information. — Rufus L, Jun 10 '19 at 15:55
I have look at this link but I still don't understand why I can't get my image to stay as jpeg? — Rae, Jun 10 '19 at 15:56
@Rae [`System.Drawing.Bitmap`](https://learn.microsoft.com/en-us/dotnet/api/system.drawing.bitmap?view=netframework-4.8) is a class, not a file format. It represents the bits that form your image. — Rufus L, Jun 10 '19 at 15:58
It's not clear where `item.Value` comes from, but if it's from the browser, beware of [path traversal attacks](https://www.owasp.org/index.php/Path_Traversal). Check that the resulting filepath is under the directory that you expect it to be. — spender, Jun 10 '19 at 16:10

Rhaokiel · Accepted Answer · 2019-06-10T16:00:46.470

2

In the case of C# code, the class Bitmap refers to any image that uses pixel arranged colors into a map of bits. This is not limited to files with the extension .bmp (Windows Bitmap). Examples that are Bitmaps: JPG, PNG, GIF, BMP.

As opposed to image files that contain a set of instructions to build the image such as SVG (Scalable Vector Graphics) or WMF (Windows Metafile Image). These are examples of images that are not Bitmaps.

edited Jun 10 '19 at 16:00

answered Jun 10 '19 at 15:57

Rhaokiel

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Thanks for explaining. I see now that Bitmap includes JPG. I marked this as the answer as soon as it lets me! is there a way to load my bitmap to an actual image? – Rae Jun 10 '19 at 15:59
1

As the documentation shows (https://learn.microsoft.com/en-us/dotnet/api/system.drawing.bitmap) the class Bitmap overrides the class Image. So any System.Drawing.Bitmap instance will work as the type System.Drawing.Image in any context. – Rhaokiel Jun 10 '19 at 16:02
Thank you @Rhaokiel – Rae Jun 10 '19 at 16:10

Why does Image.FromFile return System.Drawing.Bitmap?

1 Answers1