fast way to read height width and file size of jpeg without decoding

Question

I have a list of jpegs that I need to check if they are under 4096px and if the file size is below 4MB. I don't need to display the image so loading the full file and decoding it is a bit overkill.

is it possible to get only height, width from metadata and file size?

on mac os with swift

Answer 1

The file size could be checked by FileManager API.

Image width and height could be checked via CGImageSource functions (ImageIO.framework) without loading the image to memory:

do {
    let attribute = try FileManager.default.attributesOfItem(atPath: filePath)

    // Filesize
    let fileSize = attribute[FileAttributeKey.size] as! Int

    // Width & Height
    let imageFileUrl = URL(fileURLWithPath: filePath)
    if let imageSource = CGImageSourceCreateWithURL(imageFileUrl as CFURL, nil) {
        if let imageProperties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, nil) as Dictionary? {

            let width = imageProperties[kCGImagePropertyPixelWidth] as! Int
            let height = imageProperties[kCGImagePropertyPixelHeight] as! Int

            if (height > 4096 || width > 4096 || height < 256 || width < 256) {
                print("Size not valid")
            } else {
                print("Size is valid")
            }
        }
    }

} catch {
    print("File attributes cannot be read")
}