Free file locked by new Bitmap(filePath)
Here is my approach to opening an image without locking the file...
public static Image FromFile(string path)
{
var bytes = File.ReadAllBytes(path);
var ms = new MemoryStream(bytes);
var img = Image.FromStream(ms);
return img;
}
UPDATE: I did some perf tests to see which method was the fastest. I compared it to @net_progs "copy from bitmap" answer (which seems to be the closest to correct, though does have some issues). I loaded the image 10000 times for each method and calculated the average time per image. Here are the results:
Loading from bytes: ~0.26 ms per image.
Copying from bitmap: ~0.50 ms per image.
The results seem to make sense since you have to create the image twice using the copy from bitmap method.
UPDATE: if you need a BitMap you can do:
return (Bitmap)Image.FromStream(ms);
This is a common locking question widely discussed over the web.
The suggested trick with stream will not work, actually it works initially, but causes problems later. For example, it will load the image and the file will remain unlocked, but if you try to save the loaded image via Save() method, it will throw a generic GDI+ exception.
Next, the way with per pixel replication doesn't seem to be solid, at least it is noisy.
What I found working is described here: http://www.eggheadcafe.com/microsoft/Csharp/35017279/imagefromfile--locks-file.aspx
This is how the image should be loaded:
Image img;
using (var bmpTemp = new Bitmap("image_file_path"))
{
img = new Bitmap(bmpTemp);
}
I was looking for a solution to this problem and this method works fine for me so far, so I decided to describe it, since I found that many people advise the incorrect stream approach here and over the web.
Using a filestream will unlock the file once it has been read from and disposed:
using (var fs = new System.IO.FileStream("c:\\path to file.bmp", System.IO.FileMode.Open))
{
var bmp = new Bitmap(fs);
pct.Image = (Bitmap) bmp.Clone();
}
Edit: Updated to allow the original bitmap to be disposed, and allow the FileStream to be closed.
THIS ANSWER IS NOT SAFE - See comments, and see discussion in net_prog's answer. The Edit to use Clone
does not make it any safer - Clone clones all fields, including the filestream reference, which in certain circumstances will cause a problem.