# QLPreviewRequestCreateContext(_:_:_:_:) Creates a graphics context to draw the preview in. ``` func QLPreviewRequestCreateContext(_ preview: QLPreviewRequest!, _ size: CGSize, _ isBitmap: Bool, _ properties: CFDictionary!) -> Unmanaged! ``` ## Parameters `preview` The preview request object. `size` The size of the preview; if `isBitmap` is `true` the size is in pixels, otherwise it’s in points. `isBitmap` `true` if the preview uses a bitmap-based graphics context, `false` otherwise. This value of this parameter affects the interpretation of the `size` parameter. `properties` A dictionary containing properties for the preview response. `Preview Properties` lists the current property keys and describes their values. ## Return Value A Core Graphics graphics-context object that you can draw your preview image in. You should explicitly release this object when it is no longer needed. ## Discussion You can directly draw your preview data in the graphics-context object created by this function. After calling this function, you should flush the context with [`QLPreviewRequestFlushContext(_:_:)`](/documentation/QuickLook/QLPreviewRequestFlushContext(_:_:)). Also be sure to release the `CGContext` object. Quick Look provides three types of graphics contexts for drawing previews: bitmap, single-page vector-based, and multi-page vector-based (for PDF previews). You use this function to acquire a context for bitmap and single-page vector drawing; the `isBitmap` parameter is used to distinguish between them. For multi-page contexts, use the [`QLPreviewRequestCreatePDFContext(_:_:_:_:)`](/documentation/QuickLook/QLPreviewRequestCreatePDFContext(_:_:_:_:)) function. 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 preview request is made in; generally, this is the same thread in which the `GeneratePreviewForURL` 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)