# startTask(toRender:from:to:at:) Renders a portion of an image to a point in the destination. ``` func startTask(toRender image: CIImage, from fromRect: CGRect, to destination: CIRenderDestination, at atPoint: CGPoint) throws -> CIRenderTask ``` ## Parameters `image` A [`CIImage`](/documentation/CoreImage/CIImage) to render. `fromRect` The part of the image to render, as if cropped. `destination` A [`CIRenderDestination`](/documentation/CoreImage/CIRenderDestination) into which to render the image. `atPoint` An origin point in the destination at which to place the image. ## Return Value An asynchronous [`CIRenderTask`](/documentation/CoreImage/CIRenderTask) to render the image to the specified destination. ## Discussion This method crops the image to the specified rectangle and renders the result at the indicated origin point. If the image’s [`extent`](/documentation/CoreImage/CIImage/extent) property and `fromRect` argument values are infinite, this call renders the image’s (0, 0) point starting from the origin `atPoint`. You must use an -backed [`CIContext`](/documentation/CoreImage/CIContext) to support an -backed [`CIRenderDestination`](/documentation/CoreImage/CIRenderDestination). Similarly, you must use `GLContext`-backed [`CIContext`](/documentation/CoreImage/CIContext) to support a `GLTexture`-backed [`CIRenderDestination`](/documentation/CoreImage/CIRenderDestination). This call returns as soon as it enqueues all work required to render the image on the context’s device. In many situations, after issuing a render, you may need to wait for it to complete. In these cases, use the returned [`CIRenderTask`](/documentation/CoreImage/CIRenderTask) as follows: ```swift let renderTask = try context.startTask(toRender: image, from: fromRect, to: destination, at: point) let renderInfo = try renderTask.waitUntilCompleted() ``` --- 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)