CGImageSourceCreateThumbnailAtIndex(_:_:_:)
Creates a thumbnail version of the image at the specified index in an image source.
Declaration
func CGImageSourceCreateThumbnailAtIndex(_ isrc: CGImageSource, _ index: Int, _ options: CFDictionary?) -> CGImage?Parameters
- isrc:
The image source that contains the image data.
- index:
The zero-based index of the image you want. If the index is invalid, this method returns
NULL. - options:
A dictionary that specifies additional creation options. For a list of possible values, see Cgimagesource.
Return Value
The image at the specified index, or NULL if an error occurs. You are responsible for releasing the returned object using CGImageRelease.
Discussion
If the image source is a PDF, this function creates a 72 dpi image of the PDF page specified by the index that you pass. You must, however, pass an options dictionary that contains either the kCGImageSourceCreateThumbnailFromImageIfAbsent or kCGImageSourceCreateThumbnailFromImageAlways keys, with the value of the key set to true.