# Alpha compositing Composite images together. ## Topics ### Performing nonpremultiplied alpha compositing [`vImageAlphaBlend_Planar8(_:_:_:_:_:_:_:)`](/documentation/Accelerate/vImageAlphaBlend_Planar8(_:_:_:_:_:_:_:)) Performs nonpremultiplied alpha compositing of two 8-bit planar buffers. [`vImageAlphaBlend_PlanarF(_:_:_:_:_:_:_:)`](/documentation/Accelerate/vImageAlphaBlend_PlanarF(_:_:_:_:_:_:_:)) Performs nonpremultiplied alpha compositing of two 8-bit planar buffers. [`vImageAlphaBlend_ARGB8888(_:_:_:_:)`](/documentation/Accelerate/vImageAlphaBlend_ARGB8888(_:_:_:_:)) Performs nonpremultiplied alpha compositing of two 8-bit-per-channel, 4-channel ARGB buffers. [`vImageAlphaBlend_ARGBFFFF(_:_:_:_:)`](/documentation/Accelerate/vImageAlphaBlend_ARGBFFFF(_:_:_:_:)) Performs nonpremultiplied alpha compositing of two 32-bit-per-channel, 4-channel ARGB buffers. ### Performing premultiplied alpha compositing [`vImagePremultipliedAlphaBlend_Planar8(_:_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedAlphaBlend_Planar8(_:_:_:_:_:)) Performs premultiplied alpha compositing of two 8-bit planar buffers. [`vImagePremultipliedAlphaBlend_PlanarF(_:_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedAlphaBlend_PlanarF(_:_:_:_:_:)) Performs premultiplied alpha compositing of two 32-bit planar buffers. [`vImagePremultipliedAlphaBlend_ARGB8888(_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedAlphaBlend_ARGB8888(_:_:_:_:)) Performs premultiplied alpha compositing of two 8-bit-per-channel, 4-channel ARGB buffers. [`vImagePremultipliedAlphaBlend_ARGBFFFF(_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedAlphaBlend_ARGBFFFF(_:_:_:_:)) Performs premultiplied alpha compositing of two 32-bit-per-channel, 4-channel ARGB buffers. [`vImagePremultipliedAlphaBlend_BGRA8888(_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedAlphaBlend_BGRA8888(_:_:_:_:)) Performs premultiplied alpha compositing of two 8-bit-per-channel, 4-channel BGRA buffers. [`vImagePremultipliedAlphaBlend_RGBA8888`](/documentation/Accelerate/vImagePremultipliedAlphaBlend_RGBA8888) Performs premultiplied alpha compositing of two 8-bit-per-channel, 4-channel RGBA buffers. [`vImagePremultipliedAlphaBlend_BGRAFFFF(_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedAlphaBlend_BGRAFFFF(_:_:_:_:)) Performs premultiplied alpha compositing of two 32-bit-per-channel, 4-channel BGRA buffers. [`vImagePremultipliedAlphaBlend_RGBAFFFF`](/documentation/Accelerate/vImagePremultipliedAlphaBlend_RGBAFFFF) Performs premultiplied alpha compositing of two 32-bit-per-channel, 4-channel RGBA buffers. ### Performing premultiplied alpha compositing with blend modes [`vImagePremultipliedAlphaBlendLighten_RGBA8888(_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedAlphaBlendLighten_RGBA8888(_:_:_:_:)) Performs alpha compositing of two 8-bit-per-channel, 4-channel BGRA buffers using the lighten blend mode. [`vImagePremultipliedAlphaBlendDarken_RGBA8888(_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedAlphaBlendDarken_RGBA8888(_:_:_:_:)) Performs alpha compositing of two 8-bit-per-channel, 4-channel BGRA buffers using the darken blend mode. [`vImagePremultipliedAlphaBlendScreen_RGBA8888(_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedAlphaBlendScreen_RGBA8888(_:_:_:_:)) Performs alpha compositing of two 8-bit-per-channel, 4-channel BGRA buffers using the screen blend mode. [`vImagePremultipliedAlphaBlendMultiply_RGBA8888(_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedAlphaBlendMultiply_RGBA8888(_:_:_:_:)) Performs alpha compositing of two 8-bit-per-channel, 4-channel BGRA buffers using the multiply blend mode. ### Performing premultiplied alpha compositing with a permute [`vImagePremultipliedAlphaBlendWithPermute_ARGB8888(_:_:_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedAlphaBlendWithPermute_ARGB8888(_:_:_:_:_:_:)) Permutes the top 8-bit, 4-channel premultiplied buffer, and composites with the bottom buffer. [`vImagePremultipliedAlphaBlendWithPermute_RGBA8888(_:_:_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedAlphaBlendWithPermute_RGBA8888(_:_:_:_:_:_:)) Permutes the top 8-bit, 4-channel premultiplied buffer, and composites with the bottom buffer. ### Performing premultiplied alpha compositing with a single alpha value [`vImagePremultipliedConstAlphaBlend_Planar8(_:_:_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedConstAlphaBlend_Planar8(_:_:_:_:_:_:)) Performs premultiplied alpha compositing of two 8-bit planar buffers and applies an extra alpha value to the top buffer. [`vImagePremultipliedConstAlphaBlend_PlanarF(_:_:_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedConstAlphaBlend_PlanarF(_:_:_:_:_:_:)) Performs premultiplied alpha compositing of two 32-bit planar buffers and applies an extra alpha value to the top buffer. [`vImagePremultipliedConstAlphaBlend_ARGB8888(_:_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedConstAlphaBlend_ARGB8888(_:_:_:_:_:)) Performs premultiplied alpha compositing of two 8-bit-per-channel, 4-channel interleaved buffers and applies an extra alpha value to the top buffer. [`vImagePremultipliedConstAlphaBlend_ARGBFFFF(_:_:_:_:_:)`](/documentation/Accelerate/vImagePremultipliedConstAlphaBlend_ARGBFFFF(_:_:_:_:_:)) Performs premultiplied alpha compositing of two 32-bit-per-channel, 4-channel interleaved buffers and applies an extra alpha value to the top buffer. ### Performing nonpremultiplied to premultiplied alpha compositing [`vImageAlphaBlend_NonpremultipliedToPremultiplied_Planar8(_:_:_:_:_:)`](/documentation/Accelerate/vImageAlphaBlend_NonpremultipliedToPremultiplied_Planar8(_:_:_:_:_:)) Composites a nonpremultiplied 8-bit planar buffer over a premultiplied 8-bit planar buffer and generates a premultiplied result. [`vImageAlphaBlend_NonpremultipliedToPremultiplied_PlanarF(_:_:_:_:_:)`](/documentation/Accelerate/vImageAlphaBlend_NonpremultipliedToPremultiplied_PlanarF(_:_:_:_:_:)) Composites a nonpremultiplied 32-bit planar buffer over a premultiplied 32-bit planar buffer and generates a premultiplied result. [`vImageAlphaBlend_NonpremultipliedToPremultiplied_ARGB8888(_:_:_:_:)`](/documentation/Accelerate/vImageAlphaBlend_NonpremultipliedToPremultiplied_ARGB8888(_:_:_:_:)) Composites a nonpremultiplied 8-bit-per-channel, ARGB buffer over a premultiplied ARGB buffer and generates a premultiplied result. [`vImageAlphaBlend_NonpremultipliedToPremultiplied_ARGBFFFF(_:_:_:_:)`](/documentation/Accelerate/vImageAlphaBlend_NonpremultipliedToPremultiplied_ARGBFFFF(_:_:_:_:)) Composites a nonpremultiplied 32-bit-per-channel, ARGB buffer over a premultiplied ARGB buffer and generates a premultiplied result. ### Converting from unpremultiplied to premultiplied format [`vImagePremultiplyData_Planar8(_:_:_:_:)`](/documentation/Accelerate/vImagePremultiplyData_Planar8(_:_:_:_:)) Transforms an 8-bit planar buffer from nonpremultiplied alpha format to premultiplied alpha format. [`vImagePremultiplyData_PlanarF(_:_:_:_:)`](/documentation/Accelerate/vImagePremultiplyData_PlanarF(_:_:_:_:)) Transforms a 32-bit planar buffer from nonpremultiplied alpha format to premultiplied alpha format. [`vImagePremultiplyData_ARGB8888(_:_:_:)`](/documentation/Accelerate/vImagePremultiplyData_ARGB8888(_:_:_:)) Transforms an 8-bit-per-channel, 4-channel ARGB buffer from nonpremultiplied alpha format to premultiplied alpha format. [`vImagePremultiplyData_RGBA8888(_:_:_:)`](/documentation/Accelerate/vImagePremultiplyData_RGBA8888(_:_:_:)) Transforms an 8-bit-per-channel, 4-channel RGBA buffer from nonpremultiplied alpha format to premultiplied alpha format. [`vImagePremultiplyData_BGRA8888`](/documentation/Accelerate/vImagePremultiplyData_BGRA8888) Transforms an 8-bit-per-channel, 4-channel BGRA buffer from nonpremultiplied alpha format to premultiplied alpha format. [`vImagePremultiplyData_ARGB16U(_:_:_:)`](/documentation/Accelerate/vImagePremultiplyData_ARGB16U(_:_:_:)) Transforms an unsigned 16-bit-per-channel, 4-channel ARGB buffer from nonpremultiplied alpha format to premultiplied alpha format. [`vImagePremultiplyData_RGBA16U(_:_:_:)`](/documentation/Accelerate/vImagePremultiplyData_RGBA16U(_:_:_:)) Transforms an unsigned 16-bit-per-channel, 4-channel RGBA buffer from nonpremultiplied alpha format to premultiplied alpha format. [`vImagePremultiplyData_RGBA16F(_:_:_:)`](/documentation/Accelerate/vImagePremultiplyData_RGBA16F(_:_:_:)) Transforms a floating-point 16-bit-per-channel, 4-channel RGBA buffer from nonpremultiplied alpha format to premultiplied alpha format. [`vImagePremultiplyData_ARGB16Q12(_:_:_:)`](/documentation/Accelerate/vImagePremultiplyData_ARGB16Q12(_:_:_:)) Transforms a fixed-point 16-bit-per-channel, 4-channel ARGB buffer from nonpremultiplied alpha format to premultiplied alpha format. [`vImagePremultiplyData_RGBA16Q12(_:_:_:)`](/documentation/Accelerate/vImagePremultiplyData_RGBA16Q12(_:_:_:)) Transforms a fixed-point 16-bit-per-channel, 4-channel RGBA buffer from nonpremultiplied alpha format to premultiplied alpha format. [`vImagePremultiplyData_ARGBFFFF(_:_:_:)`](/documentation/Accelerate/vImagePremultiplyData_ARGBFFFF(_:_:_:)) Transforms a floating-point 32-bit-per-channel, 4-channel ARGB buffer from nonpremultiplied alpha format to premultiplied alpha format. [`vImagePremultiplyData_RGBAFFFF(_:_:_:)`](/documentation/Accelerate/vImagePremultiplyData_RGBAFFFF(_:_:_:)) Transforms a floating-point 32-bit-per-channel, 4-channel ARGB buffer from nonpremultiplied alpha format to premultiplied alpha format. [`vImagePremultiplyData_BGRAFFFF`](/documentation/Accelerate/vImagePremultiplyData_BGRAFFFF) Transforms a floating-point 32-bit-per-channel, 4-channel BGRA buffer from nonpremultiplied alpha format to premultiplied alpha format. ### Converting from premultiplied to unpremultiplied format [`vImageUnpremultiplyData_Planar8(_:_:_:_:)`](/documentation/Accelerate/vImageUnpremultiplyData_Planar8(_:_:_:_:)) Transforms an 8-bit planar buffer from premultiplied alpha format to nonpremultiplied alpha format. [`vImageUnpremultiplyData_PlanarF(_:_:_:_:)`](/documentation/Accelerate/vImageUnpremultiplyData_PlanarF(_:_:_:_:)) Transforms a 32-bit planar buffer from premultiplied alpha format to nonpremultiplied alpha format. [`vImageUnpremultiplyData_ARGB8888(_:_:_:)`](/documentation/Accelerate/vImageUnpremultiplyData_ARGB8888(_:_:_:)) Transforms an 8-bit-per-channel, 4-channel ARGB buffer from premultiplied alpha format to nonpremultiplied alpha format. [`vImageUnpremultiplyData_RGBA8888(_:_:_:)`](/documentation/Accelerate/vImageUnpremultiplyData_RGBA8888(_:_:_:)) Transforms an 8-bit-per-channel, 4-channel RGBA buffer from premultiplied alpha format to nonpremultiplied alpha format. [`vImageUnpremultiplyData_BGRA8888`](/documentation/Accelerate/vImageUnpremultiplyData_BGRA8888) Transforms an 8-bit-per-channel, 4-channel BGRA buffer from premultiplied alpha format to nonpremultiplied alpha format. [`vImageUnpremultiplyData_ARGB16U(_:_:_:)`](/documentation/Accelerate/vImageUnpremultiplyData_ARGB16U(_:_:_:)) Transforms an unsigned 16-bit-per-channel, 4-channel ARGB buffer from premultiplied alpha format to nonpremultiplied alpha format. [`vImageUnpremultiplyData_RGBA16U(_:_:_:)`](/documentation/Accelerate/vImageUnpremultiplyData_RGBA16U(_:_:_:)) Transforms an unsigned 16-bit-per-channel, 4-channel RGBA buffer from premultiplied alpha format to nonpremultiplied alpha format. [`vImageUnpremultiplyData_RGBA16F(_:_:_:)`](/documentation/Accelerate/vImageUnpremultiplyData_RGBA16F(_:_:_:)) Transforms a floating-point 16-bit-per-channel, 4-channel RGBA buffer from premultiplied alpha format to nonpremultiplied alpha format. [`vImageUnpremultiplyData_ARGB16Q12(_:_:_:)`](/documentation/Accelerate/vImageUnpremultiplyData_ARGB16Q12(_:_:_:)) Transforms a fixed-point 16-bit-per-channel, 4-channel ARGB buffer from premultiplied alpha format to nonpremultiplied alpha format. [`vImageUnpremultiplyData_RGBA16Q12(_:_:_:)`](/documentation/Accelerate/vImageUnpremultiplyData_RGBA16Q12(_:_:_:)) Transforms a fixed-point 16-bit-per-channel, 4-channel RGBA buffer from premultiplied alpha format to nonpremultiplied alpha format. [`vImageUnpremultiplyData_ARGBFFFF(_:_:_:)`](/documentation/Accelerate/vImageUnpremultiplyData_ARGBFFFF(_:_:_:)) Transforms a 32-bit-per-channel, 4-channel ARGB buffer from premultiplied alpha format to nonpremultiplied alpha format. [`vImageUnpremultiplyData_RGBAFFFF(_:_:_:)`](/documentation/Accelerate/vImageUnpremultiplyData_RGBAFFFF(_:_:_:)) Transforms a 32-bit-per-channel, 4-channel RGBA buffer from premultiplied alpha format to nonpremultiplied alpha format. [`vImageUnpremultiplyData_BGRAFFFF`](/documentation/Accelerate/vImageUnpremultiplyData_BGRAFFFF) Transforms a 32-bit-per-channel, 4-channel BGRA buffer from premultiplied alpha format to nonpremultiplied alpha format. ### Clipping color values to alpha [`vImageClipToAlpha_Planar8(_:_:_:_:)`](/documentation/Accelerate/vImageClipToAlpha_Planar8(_:_:_:_:)) Clamps the values of an 8-bit planar buffer to the corresponding alpha values. [`vImageClipToAlpha_PlanarF(_:_:_:_:)`](/documentation/Accelerate/vImageClipToAlpha_PlanarF(_:_:_:_:)) Clamps the values of a 32-bit planar buffer to the corresponding alpha values. [`vImageClipToAlpha_ARGB8888(_:_:_:)`](/documentation/Accelerate/vImageClipToAlpha_ARGB8888(_:_:_:)) Clamps the values of an 8-bit-per-channel, 4-channel ARGB buffer to the corresponding alpha values. [`vImageClipToAlpha_RGBA8888(_:_:_:)`](/documentation/Accelerate/vImageClipToAlpha_RGBA8888(_:_:_:)) Clamps the values of an 8-bit-per-channel, 4-channel RGBA buffer to the corresponding alpha values. [`vImageClipToAlpha_ARGBFFFF(_:_:_:)`](/documentation/Accelerate/vImageClipToAlpha_ARGBFFFF(_:_:_:)) Clamps the values of a 32-bit-per-channel, 4-channel ARGB buffer to the corresponding alpha values. [`vImageClipToAlpha_RGBAFFFF(_:_:_:)`](/documentation/Accelerate/vImageClipToAlpha_RGBAFFFF(_:_:_:)) Clamps the values of a 32-bit-per-channel, 4-channel RGBA buffer to the corresponding alpha values. ## See Also --- 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)