Posts tagged error

In GDI+ you can call Image.FromFile to load an image from a file. BUT there are several issues with this call, the biggest being that GDI+ will keep the file open long after you are done with it. Here is an image loader that gets around this issue.

If you are running a high volume web site, and your images are on a SAN you’ll find this technique necessary to prevent an eventual exhaustion of filehandles.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using System.IO;
using System.Data;

namespace Utility
{
public static class ImageLoader
{
// This isn’t going to help much – you’ll run out of memory anyway on very large images – but if you are keeping several in memory it might …
public const int MaximumImageDimension = 10000;

///
/// Method to safely load an image from a file without leaving the file open,
/// also gets the size down to a manageable size in the case of HUGE images
///
/// An Image – don’t forget to dispose of it later
public static Image LoadImage (string filePath)
{
try
{
FileInfo fi = new FileInfo(filePath);

if (!fi.Exists) throw new FileNotFoundException(“Cannot find image”);
if (fi.Length == 0) throw new FileNotFoundException(“Zero length image file “);

// Image.FromFile is known to leave files open, so we use a stream instead to read it
using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read))
{
if (!fs.CanRead) throw new FileLoadException (“Cannot read file stream”);

if (fs.Length == 0) throw new FileLoadException(“File stream zero length”);

using (Image original = Image.FromStream(fs))
{
// Make a copy of the file in memory, then release the one GDI+ gave us
// thus ensuring that all file handles are closed properly (which GDI+ doesn’t do for us in a timely fashion)
int width = original.Width;
int height = original.Height;
if (width == 0) throw new DataException(“Bad image dimension width=0″);
if (height == 0) throw new DataException(“Bad image dimension height=0″);

// Now shrink it to Max size to control memory consumption
if (width > MaximumImageDimension)
{
height = height * MaximumImageDimension / width;
width = MaximumImageDimension;
}
if (height > MaximumImageDimension)
{
width = width * MaximumImageDimension / height;
height = MaximumImageDimension;
}

Bitmap copy = new Bitmap(width, height);
using (Graphics graphics = Graphics.FromImage(copy))
{
graphics.DrawImage(original, 0, 0, copy.Width, copy.Height);
}
return copy;
}
}
}
catch (Exception ex)
{
ex.Data.Add(“FileName”, filePath);
throw;
}
}
}