# Calculating and transforming histograms Enhance and adjust the contrast of an image with histogram equalization, contrast stretching, and specification. ## Topics ### Contrast stretching [`func contrastStretch(destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/contrastStretch(destination:)-6usbh) Stretches the histogram of an 8-bit planar pixel buffer. [`func contrastStretch(binCount: Int, destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/contrastStretch(binCount:destination:)-3bo13) Stretches the histogram of a 32-bit planar pixel buffer. [`func contrastStretch(destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/contrastStretch(destination:)-7zo9) Stretches the histogram of an 8-bit-per-channel, 4-channel interleaved pixel buffer. [`func contrastStretch(binCount: Int, destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/contrastStretch(binCount:destination:)-704t6) Stretches the histogram of a 32-bit-per-channel, 4-channel interleaved pixel buffer. [`func contrastStretch(destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/contrastStretch(destination:)-2nsx9) Stretches the histogram of a multiple-plane 8-bit pixel buffer. [`func contrastStretch(binCount: Int, destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/contrastStretch(binCount:destination:)-81vq2) Stretches the histogram of a multiple-plane 32-bit pixel buffer. ### Equalization [`func equalizeHistogram(destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/equalizeHistogram(destination:)-7temg) Equalizes the histogram of an 8-bit planar pixel buffer. [`func equalizeHistogram(binCount: Int, destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/equalizeHistogram(binCount:destination:)-5iv0q) Equalizes the histogram of a 32-bit planar pixel buffer. [`func equalizeHistogram(destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/equalizeHistogram(destination:)-2gbmf) Equalizes the histogram of an 8-bit-per-channel, 4-channel interleaved pixel buffer. [`func equalizeHistogram(binCount: Int, destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/equalizeHistogram(binCount:destination:)-6on8w) Equalizes the histogram of a 32-bit-per-channel, 4-channel interleaved pixel buffer. [`func equalizeHistogram(destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/equalizeHistogram(destination:)-939xn) Equalizes the histogram of a multiple-plane 8-bit pixel buffer. [`func equalizeHistogram(binCount: Int, destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/equalizeHistogram(binCount:destination:)-59li2) Equalizes the histogram of a multiple-plane 32-bit pixel buffer. ### Histogram calculation [`func histogram() -> vImage.PixelBuffer.Histogram8888`](/documentation/Accelerate/vImage/PixelBuffer/histogram()-14a38) Calculates the histogram of an 8-bit-per-channel, 4-channel interleaved pixel buffer. [`func histogram(binCount: Int) -> vImage.PixelBuffer.HistogramFFFF`](/documentation/Accelerate/vImage/PixelBuffer/histogram(binCount:)-6pkfv) Calculates the histogram of a 32-bit-per-channel, 4-channel interleaved pixel buffer. [`func histogram() -> vImage.PixelBuffer.Histogram888`](/documentation/Accelerate/vImage/PixelBuffer/histogram()-30tsp) Calculates the histogram of an 8-bit-per-channel, 3-channel multiple-plane pixel buffer. [`func histogram(binCount: Int) -> vImage.PixelBuffer.HistogramFFF`](/documentation/Accelerate/vImage/PixelBuffer/histogram(binCount:)-8wymg) Calculates the histogram of a 32-bit-per-channel, 3-channel multiple-plane pixel buffer. [`func histogram() -> vImage.PixelBuffer.Histogram8888`](/documentation/Accelerate/vImage/PixelBuffer/histogram()-6wxl5) Calculates the histogram of an 8-bit-per-channel, 4-channel multiple-plane pixel buffer. [`func histogram(binCount: Int) -> vImage.PixelBuffer.HistogramFFFF`](/documentation/Accelerate/vImage/PixelBuffer/histogram(binCount:)-5bqka) Calculates the histogram of a 32-bit-per-channel, 4-channel multiple-plane pixel buffer. ### Histogram specification [`func specifyHistogram(vImage.PixelBuffer.Histogram8888, destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/specifyHistogram(_:destination:)-7xiz4) Performs a histogram specification operation on an 8-bit-per-channel, 4-channel interleaved pixel buffer. [`func specifyHistogram(vImage.PixelBuffer.HistogramFFFF, destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/specifyHistogram(_:destination:)-1x46n) Performs a histogram specification operation on a 32-bit-per-channel, 4-channel interleaved pixel buffer. [`func specifyHistogram(vImage.PixelBuffer.Histogram888, destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/specifyHistogram(_:destination:)-qeqr) Performs a histogram specification operation on an 8-bit-per-channel, 3-channel multiple-plane pixel buffer. [`func specifyHistogram(vImage.PixelBuffer.HistogramFFF, destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/specifyHistogram(_:destination:)-28844) Performs a histogram specification operation on a 32-bit-per-channel, 3-channel multiple-plane pixel buffer. [`func specifyHistogram(vImage.PixelBuffer.Histogram8888, destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/specifyHistogram(_:destination:)-73dpr) Performs a histogram specification operation on an 8-bit-per-channel, 4-channel multiple-plane pixel buffer. [`func specifyHistogram(vImage.PixelBuffer.HistogramFFFF, destination: vImage.PixelBuffer)`](/documentation/Accelerate/vImage/PixelBuffer/specifyHistogram(_:destination:)-7cvk1) Performs a histogram specification operation on a 32-bit-per-channel, 3-channel multiple-plane pixel buffer. ### Type aliases [`typealias Histogram888`](/documentation/Accelerate/vImage/PixelBuffer/Histogram888) The histogram for three channel 8-bit pixel buffers. [`typealias Histogram8888`](/documentation/Accelerate/vImage/PixelBuffer/Histogram8888) The histogram for four channel 8-bit pixel buffers. [`typealias HistogramFFF`](/documentation/Accelerate/vImage/PixelBuffer/HistogramFFF) The histogram for three channel 32-bit pixel buffers. [`typealias HistogramFFFF`](/documentation/Accelerate/vImage/PixelBuffer/HistogramFFFF) The histogram for four channel 32-bit pixel buffers. --- 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)