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Merge pull request #1771 from nextcloud/blurhash
Add blurhash as placeholder
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,151 @@ | ||
| // | ||
| // SPDX-FileCopyrightText: 2018 Wolt Enterprises | ||
| // SPDX-License-Identifier: MIT | ||
| // | ||
|
|
||
| import UIKit | ||
|
|
||
| extension UIImage { | ||
| public convenience init?(blurHash: String, size: CGSize, punch: Float = 1) { | ||
| guard blurHash.count >= 6 else { return nil } | ||
|
|
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| let sizeFlag = String(blurHash[0]).decode83() | ||
| let numY = (sizeFlag / 9) + 1 | ||
| let numX = (sizeFlag % 9) + 1 | ||
|
|
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| let quantisedMaximumValue = String(blurHash[1]).decode83() | ||
| let maximumValue = Float(quantisedMaximumValue + 1) / 166 | ||
|
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| guard blurHash.count == 4 + 2 * numX * numY else { return nil } | ||
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| let colours: [(Float, Float, Float)] = (0 ..< numX * numY).map { i in | ||
| if i == 0 { | ||
| let value = String(blurHash[2 ..< 6]).decode83() | ||
| return decodeDC(value) | ||
| } else { | ||
| let value = String(blurHash[4 + i * 2 ..< 4 + i * 2 + 2]).decode83() | ||
| return decodeAC(value, maximumValue: maximumValue * punch) | ||
| } | ||
| } | ||
|
|
||
| let width = Int(size.width) | ||
| let height = Int(size.height) | ||
| let bytesPerRow = width * 3 | ||
| guard let data = CFDataCreateMutable(kCFAllocatorDefault, bytesPerRow * height) else { return nil } | ||
| CFDataSetLength(data, bytesPerRow * height) | ||
| guard let pixels = CFDataGetMutableBytePtr(data) else { return nil } | ||
|
|
||
| for y in 0 ..< height { | ||
| for x in 0 ..< width { | ||
| var r: Float = 0 | ||
| var g: Float = 0 | ||
| var b: Float = 0 | ||
|
|
||
| for j in 0 ..< numY { | ||
| for i in 0 ..< numX { | ||
| let basis = cos(Float.pi * Float(x) * Float(i) / Float(width)) * cos(Float.pi * Float(y) * Float(j) / Float(height)) | ||
| let colour = colours[i + j * numX] | ||
| r += colour.0 * basis | ||
| g += colour.1 * basis | ||
| b += colour.2 * basis | ||
| } | ||
| } | ||
|
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||
| let intR = UInt8(linearTosRGB(r)) | ||
| let intG = UInt8(linearTosRGB(g)) | ||
| let intB = UInt8(linearTosRGB(b)) | ||
|
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||
| pixels[3 * x + 0 + y * bytesPerRow] = intR | ||
| pixels[3 * x + 1 + y * bytesPerRow] = intG | ||
| pixels[3 * x + 2 + y * bytesPerRow] = intB | ||
| } | ||
| } | ||
|
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| let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue) | ||
|
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| guard let provider = CGDataProvider(data: data) else { return nil } | ||
| guard let cgImage = CGImage(width: width, height: height, bitsPerComponent: 8, bitsPerPixel: 24, bytesPerRow: bytesPerRow, | ||
| space: CGColorSpaceCreateDeviceRGB(), bitmapInfo: bitmapInfo, provider: provider, decode: nil, shouldInterpolate: true, intent: .defaultIntent) else { return nil } | ||
|
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| self.init(cgImage: cgImage) | ||
| } | ||
| } | ||
|
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| private func decodeDC(_ value: Int) -> (Float, Float, Float) { | ||
| let intR = value >> 16 | ||
| let intG = (value >> 8) & 255 | ||
| let intB = value & 255 | ||
| return (sRGBToLinear(intR), sRGBToLinear(intG), sRGBToLinear(intB)) | ||
| } | ||
|
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||
| private func decodeAC(_ value: Int, maximumValue: Float) -> (Float, Float, Float) { | ||
| let quantR = value / (19 * 19) | ||
| let quantG = (value / 19) % 19 | ||
| let quantB = value % 19 | ||
|
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||
| let rgb = ( | ||
| signPow((Float(quantR) - 9) / 9, 2) * maximumValue, | ||
| signPow((Float(quantG) - 9) / 9, 2) * maximumValue, | ||
| signPow((Float(quantB) - 9) / 9, 2) * maximumValue | ||
| ) | ||
|
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| return rgb | ||
| } | ||
|
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| private func signPow(_ value: Float, _ exp: Float) -> Float { | ||
| return copysign(pow(abs(value), exp), value) | ||
| } | ||
|
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| private func linearTosRGB(_ value: Float) -> Int { | ||
| let v = max(0, min(1, value)) | ||
| if v <= 0.0031308 { return Int(v * 12.92 * 255 + 0.5) } | ||
| else { return Int((1.055 * pow(v, 1 / 2.4) - 0.055) * 255 + 0.5) } | ||
| } | ||
|
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| private func sRGBToLinear<Type: BinaryInteger>(_ value: Type) -> Float { | ||
| let v = Float(Int64(value)) / 255 | ||
| if v <= 0.04045 { return v / 12.92 } | ||
| else { return pow((v + 0.055) / 1.055, 2.4) } | ||
| } | ||
|
|
||
| private let encodeCharacters: [String] = { | ||
| return "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz#$%*+,-.:;=?@[]^_{|}~".map { String($0) } | ||
| }() | ||
|
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| private let decodeCharacters: [String: Int] = { | ||
| var dict: [String: Int] = [:] | ||
| for (index, character) in encodeCharacters.enumerated() { | ||
| dict[character] = index | ||
| } | ||
| return dict | ||
| }() | ||
|
|
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| extension String { | ||
| func decode83() -> Int { | ||
| var value: Int = 0 | ||
| for character in self { | ||
| if let digit = decodeCharacters[String(character)] { | ||
| value = value * 83 + digit | ||
| } | ||
| } | ||
| return value | ||
| } | ||
| } | ||
|
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| private extension String { | ||
| subscript (offset: Int) -> Character { | ||
| return self[index(startIndex, offsetBy: offset)] | ||
| } | ||
|
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| subscript (bounds: CountableClosedRange<Int>) -> Substring { | ||
| let start = index(startIndex, offsetBy: bounds.lowerBound) | ||
| let end = index(startIndex, offsetBy: bounds.upperBound) | ||
| return self[start...end] | ||
| } | ||
|
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| subscript (bounds: CountableRange<Int>) -> Substring { | ||
| let start = index(startIndex, offsetBy: bounds.lowerBound) | ||
| let end = index(startIndex, offsetBy: bounds.upperBound) | ||
| return self[start..<end] | ||
| } | ||
| } |
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