# QLThumbnailRequestCreateContext(_:_:_:_:) Creates a graphics context to draw the thumbnail in. ``` func QLThumbnailRequestCreateContext(_ thumbnail: QLThumbnailRequest!, _ size: CGSize, _ isBitmap: Bool, _ properties: CFDictionary!) -> Unmanaged! ``` ## Parameters `size` The size of the thumbnail; if `isBitmap` is `true` the size is in pixels, otherwise it’s in points. `isBitmap` `true` if the thumbnail data is bitmap-based, `false` if vector-based. This value of this parameter affects the interpretation of the `size` parameter. `properties` A dictionary containing properties for the thumbnail response. For macOS 10.5, no properties have been defined. ## Return Value A Core Graphics graphics-context object that you can draw your thumbnail image in. You should explicitly release this object when it is no longer needed. ## Discussion You can directly draw your thumbnail data in the graphics-context object created by this function. After calling this function, you should flush the context with [`QLThumbnailRequestFlushContext(_:_:)`](/documentation/QuickLook/QLThumbnailRequestFlushContext(_:_:)). Also be sure to release the `CGContext` object. With this function you can create two types of graphics contexts for drawing thumbnails: bitmap and single-page vector-based; you use the `isBitmap` flag to distinguish between the two. Quick Look handles bitmap thumbnail context differently than non-bitmap contexts; in the latter case, Quick Look might scale the drawing up or down if necessary, and it respects the scale factor (for HiDPI support). If you prefer to work in Objective-C code, you can convert the created to a object using . ### Special Considerations Thread-safety: This function should be called in the same thread as the thumbnail request is made in; generally, this is the same thread in which the `GenerateThumbnailForURL` callback was invoked. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)