How Can I Efficiently Retrieve Image Dimensions Without Loading the Entire File?

Get image size efficiently

In many image processing tasks, determining the image size is crucial. However, the traditional method of loading the entire image file is inefficient when only size information is required.

Fortunately, there are alternative ways to get image dimensions without loading the entire file. One such technique is to analyze image header information, which often contains information such as dimensions.

To implement this method, it is recommended to use a well-tested image processing library that supports multiple image formats. If you can't use the library, you can write custom code to parse the image header.

Here is a sample code snippet that handles several common image formats:

<code>// ... (代码已省略) ...

public static Size GetDimensions(string path)
{
    using (BinaryReader br = new BinaryReader(File.OpenRead(path)))
    {
        try
        {
            return GetDimensions(br);
        }
        catch (ArgumentException e)
        {
            if (e.Message.StartsWith("无法识别图像格式。"))
            {
                throw new ArgumentException("无法识别图像格式。", "path", e);
            }
            else
            {
                throw e;
            }
        }
    }
}

// ... (代码已省略) ...

private static Size DecodeBitmap(BinaryReader br)
{
    br.ReadBytes(16);
    int width = br.ReadInt32();
    int height = br.ReadInt32();
    return new Size(width, height);
}

// ... (其他格式解码器已省略) ...</code>

This technique provides a more efficient way to obtain image dimensions, especially when working with large image files or multiple images.

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