kCGImageSourceSubsampleFactor
The factor by which to scale down any returned images.
Declaration
let kCGImageSourceSubsampleFactor: CFStringDiscussion
When you specify this key, the image source scales down the image data by the specified numerical factor. The value of this key must be a CFNumber containing the integer value 2, 4, or 8. If the image doesn’t support the specified scale factor, the image source provides a larger or full-size normal image.
Image sources support this option only for JPEG, HEIF, TIFF, and PNG images.