diff --git a/Sources/SnapshotTesting/Snapshotting/UIImage.swift b/Sources/SnapshotTesting/Snapshotting/UIImage.swift index e5fc4262..ea36c1a6 100644 --- a/Sources/SnapshotTesting/Snapshotting/UIImage.swift +++ b/Sources/SnapshotTesting/Snapshotting/UIImage.swift @@ -192,6 +192,7 @@ #endif #if os(iOS) || os(tvOS) || os(macOS) + import Accelerate.vImage import CoreImage.CIKernel import MetalPerformanceShaders @@ -199,50 +200,124 @@ func perceptuallyCompare( _ old: CIImage, _ new: CIImage, pixelPrecision: Float, perceptualPrecision: Float ) -> String? { - let deltaOutputImage = old.applyingFilter("CILabDeltaE", parameters: ["inputImage2": new]) - let thresholdOutputImage: CIImage - do { - thresholdOutputImage = try ThresholdImageProcessorKernel.apply( - withExtent: new.extent, - inputs: [deltaOutputImage], - arguments: [ - ThresholdImageProcessorKernel.inputThresholdKey: (1 - perceptualPrecision) * 100 - ] - ) - } catch { - return "Newly-taken snapshot's data could not be loaded. \(error)" - } - var averagePixel: Float = 0 + // Calculate the deltaE values. Each pixel is a value between 0-100. + // 0 means no difference, 100 means completely opposite. + let deltaOutputImage = old.applyingLabDeltaE(new) + // Setting the working color space and output color space to NSNull disables color management. This is appropriate when the output + // of the operations is computational instead of an image intended to be displayed. let context = CIContext(options: [.workingColorSpace: NSNull(), .outputColorSpace: NSNull()]) - context.render( - thresholdOutputImage.applyingFilter( - "CIAreaAverage", parameters: [kCIInputExtentKey: new.extent]), - toBitmap: &averagePixel, - rowBytes: MemoryLayout.size, - bounds: CGRect(x: 0, y: 0, width: 1, height: 1), - format: .Rf, - colorSpace: nil - ) - let actualPixelPrecision = 1 - averagePixel - guard actualPixelPrecision < pixelPrecision else { return nil } + let deltaThreshold = (1 - perceptualPrecision) * 100 + let actualPixelPrecision: Float var maximumDeltaE: Float = 0 - context.render( - deltaOutputImage.applyingFilter("CIAreaMaximum", parameters: [kCIInputExtentKey: new.extent]), - toBitmap: &maximumDeltaE, - rowBytes: MemoryLayout.size, - bounds: CGRect(x: 0, y: 0, width: 1, height: 1), - format: .Rf, - colorSpace: nil - ) - let actualPerceptualPrecision = 1 - maximumDeltaE / 100 - if pixelPrecision < 1 { - return """ - Actual image precision \(actualPixelPrecision) is less than required \(pixelPrecision) - Actual perceptual precision \(actualPerceptualPrecision) is less than required \(perceptualPrecision) - """ + + // Metal is supported by all iOS/tvOS devices (2013 models or later) and Macs (2012 models or later). + // Older devices do not support iOS/tvOS 13 and macOS 10.15 which are the minimum versions of swift-snapshot-testing. + // However, some virtualized hardware do not have GPUs and therefore do not support Metal. + // In this case, macOS falls back to a CPU-based OpenGL ES renderer that silently fails when a Metal command is issued. + // We need to check for Metal device support and fallback to CPU based vImage buffer iteration. + if ThresholdImageProcessorKernel.isSupported { + // Fast path - Metal processing + guard + let thresholdOutputImage = try? deltaOutputImage.applyingThreshold(deltaThreshold), + let averagePixel = thresholdOutputImage.applyingAreaAverage().renderSingleValue(in: context) + else { + return "Newly-taken snapshot's data could not be processed." + } + actualPixelPrecision = 1 - averagePixel + if actualPixelPrecision < pixelPrecision { + maximumDeltaE = deltaOutputImage.applyingAreaMaximum().renderSingleValue(in: context) ?? 0 + } } else { - return - "Actual perceptual precision \(actualPerceptualPrecision) is less than required \(perceptualPrecision)" + // Slow path - CPU based vImage buffer iteration + guard let buffer = deltaOutputImage.render(in: context) else { + return "Newly-taken snapshot could not be processed." + } + defer { buffer.free() } + var failingPixelCount: Int = 0 + // rowBytes must be a multiple of 8, so vImage_Buffer pads the end of each row with bytes to meet the multiple of 0 requirement. + // We must do 2D iteration of the vImage_Buffer in order to avoid loading the padding garbage bytes at the end of each row. + // + // NB: We are purposely using a verbose 'while' loop instead of a 'for in' loop. When the + // compiler doesn't have optimizations enabled, like in test targets, a `while` loop is + // significantly faster than a `for` loop for iterating through the elements of a memory + // buffer. Details can be found in [SR-6983](https://github.com/apple/swift/issues/49531) + let componentStride = MemoryLayout.stride + var line = 0 + while line < buffer.height { + defer { line += 1 } + let lineOffset = buffer.rowBytes * line + var column = 0 + while column < buffer.width { + defer { column += 1 } + let byteOffset = lineOffset + column * componentStride + let deltaE = buffer.data.load(fromByteOffset: byteOffset, as: Float.self) + if deltaE > deltaThreshold { + failingPixelCount += 1 + if deltaE > maximumDeltaE { + maximumDeltaE = deltaE + } + } + } + } + let failingPixelPercent = Float(failingPixelCount) / Float(deltaOutputImage.extent.width * deltaOutputImage.extent.height) + actualPixelPrecision = 1 - failingPixelPercent + } + + guard actualPixelPrecision < pixelPrecision else { return nil } + // The actual perceptual precision is the perceptual precision of the pixel with the highest DeltaE. + // DeltaE is in a 0-100 scale, so we need to divide by 100 to transform it to a percentage. + let minimumPerceptualPrecision = 1 - min(maximumDeltaE / 100, 1) + return """ + The percentage of pixels that match \(actualPixelPrecision) is less than required \(pixelPrecision) + The lowest perceptual color precision \(minimumPerceptualPrecision) is less than required \(perceptualPrecision) + """ + } + + extension CIImage { + func applyingLabDeltaE(_ other: CIImage) -> CIImage { + applyingFilter("CILabDeltaE", parameters: ["inputImage2": other]) + } + + func applyingThreshold(_ threshold: Float) throws -> CIImage { + try ThresholdImageProcessorKernel.apply( + withExtent: extent, + inputs: [self], + arguments: [ThresholdImageProcessorKernel.inputThresholdKey: threshold] + ) + } + + func applyingAreaAverage() -> CIImage { + applyingFilter("CIAreaAverage", parameters: [kCIInputExtentKey: extent]) + } + + func applyingAreaMaximum() -> CIImage { + applyingFilter("CIAreaMaximum", parameters: [kCIInputExtentKey: extent]) + } + + func renderSingleValue(in context: CIContext) -> Float? { + guard let buffer = render(in: context) else { return nil } + defer { buffer.free() } + return buffer.data.load(fromByteOffset: 0, as: Float.self) + } + + func render(in context: CIContext, format: CIFormat = CIFormat.Rh) -> vImage_Buffer? { + // Some hardware configurations (virtualized CPU renderers) do not support 32-bit float output formats, + // so use a compatible 16-bit float format and convert the output value to 32-bit floats. + guard var buffer16 = try? vImage_Buffer(width: Int(extent.width), height: Int(extent.height), bitsPerPixel: 16) else { return nil } + defer { buffer16.free() } + context.render( + self, + toBitmap: buffer16.data, + rowBytes: buffer16.rowBytes, + bounds: extent, + format: format, + colorSpace: nil + ) + guard + var buffer32 = try? vImage_Buffer(width: Int(buffer16.width), height: Int(buffer16.height), bitsPerPixel: 32), + vImageConvert_Planar16FtoPlanarF(&buffer16, &buffer32, 0) == kvImageNoError + else { return nil } + return buffer32 } } @@ -252,6 +327,19 @@ static let inputThresholdKey = "thresholdValue" static let device = MTLCreateSystemDefaultDevice() + static var isSupported: Bool { + guard let device = device else { + return false + } + #if targetEnvironment(simulator) + guard #available(iOS 14.0, tvOS 14.0, *) else { + // The MPSSupportsMTLDevice method throws an exception on iOS/tvOS simulators < 14.0 + return false + } + #endif + return MPSSupportsMTLDevice(device) + } + override class func process( with inputs: [CIImageProcessorInput]?, arguments: [String: Any]?, output: CIImageProcessorOutput