How to Validate Image File Format in C#
When loading an image from a file, validation is crucial to prevent errors such as OutOfMemoryExceptions. However, relying solely on file extensions can be unreliable.
Validation Function Prototypes
bool IsValidImage(string fileName); bool IsValidImage(Stream imageStream);
Solution: Image Validation Based on Byte Signatures
A reliable approach is to check the file's byte signature, which provides information about its format. Here's a C# implementation:
public enum ImageFormat
{
bmp,
jpeg,
gif,
tiff,
png,
unknown
}
public static ImageFormat GetImageFormat(byte[] bytes)
{
// Byte signatures for various image formats
var bmp = Encoding.ASCII.GetBytes("BM"); // BMP
var gif = Encoding.ASCII.GetBytes("GIF"); // GIF
var png = new byte[] { 137, 80, 78, 71 }; // PNG
var tiff = new byte[] { 73, 73, 42 }; // TIFF
var tiff2 = new byte[] { 77, 77, 42 }; // TIFF
var jpeg = new byte[] { 255, 216, 255, 224 }; // jpeg
var jpeg2 = new byte[] { 255, 216, 255, 225 }; // jpeg canon
// Compare the byte signatures to the input bytes
if (bmp.SequenceEqual(bytes.Take(bmp.Length)))
return ImageFormat.bmp;
if (gif.SequenceEqual(bytes.Take(gif.Length)))
return ImageFormat.gif;
if (png.SequenceEqual(bytes.Take(png.Length)))
return ImageFormat.png;
if (tiff.SequenceEqual(bytes.Take(tiff.Length)))
return ImageFormat.tiff;
if (tiff2.SequenceEqual(bytes.Take(tiff2.Length)))
return ImageFormat.tiff;
if (jpeg.SequenceEqual(bytes.Take(jpeg.Length)))
return ImageFormat.jpeg;
if (jpeg2.SequenceEqual(bytes.Take(jpeg2.Length)))
return ImageFormat.jpeg;
return ImageFormat.unknown;
}
Usage Examples
// Example 1: Validate an image using a file path
if (IsValidImage(filePath))
{
// Load the image safely
}
// Example 2: Validate an image using a stream
Stream imageStream = new FileStream(filePath, FileMode.Open);
if (IsValidImage(imageStream))
{
// Load the image safely
}The above is the detailed content of How to Reliably Validate Image File Formats in C#?. For more information, please follow other related articles on the PHP Chinese website!
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