551 lines
16 KiB
Swift
551 lines
16 KiB
Swift
import Foundation
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// Blurhash implementation thanks to @evanw work
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// https://github.com/evanw/thumbhash
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// NOTE: Swift has an exponential-time type checker and compiling very simple
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// expressions can easily take many seconds, especially when expressions involve
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// numeric type constructors.
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//
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// This file deliberately breaks compound expressions up into separate variables
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// to improve compile time even though this comes at the expense of readability.
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// This is a known workaround for this deficiency in the Swift compiler.
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//
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// The following command is helpful when debugging Swift compile time issues:
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//
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// swiftc ThumbHash.swift -Xfrontend -debug-time-function-bodies
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//
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// These optimizations brought the compile time for this file from around 2.5
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// seconds to around 250ms (10x faster).
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// NOTE: Swift's debug-build performance of for-in loops over numeric ranges is
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// really awful. Debug builds compile a very generic indexing iterator thing
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// that makes many nested calls for every iteration, which makes debug-build
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// performance crawl.
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//
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// This file deliberately avoids for-in loops that loop for more than a few
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// times to improve debug-build run time even though this comes at the expense
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// of readability. Similarly unsafe pointers are used instead of array getters
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// to avoid unnecessary bounds checks, which have extra overhead in debug builds.
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//
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// These optimizations brought the run time to encode and decode 10 ThumbHashes
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// in debug mode from 700ms to 70ms (10x faster).
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// swiftlint:disable all
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func rgbaToThumbHash(w: Int, h: Int, rgba: Data) -> Data {
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// Encoding an image larger than 100x100 is slow with no benefit
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assert(w <= 100 && h <= 100)
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assert(rgba.count == w * h * 4)
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// Determine the average color
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var avg_r: Float32 = 0
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var avg_g: Float32 = 0
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var avg_b: Float32 = 0
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var avg_a: Float32 = 0
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rgba.withUnsafeBytes { rgba in
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var rgba = rgba.baseAddress!.bindMemory(to: UInt8.self, capacity: rgba.count)
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let n = w * h
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var i = 0
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while i < n {
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let alpha = Float32(rgba[3]) / 255
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avg_r += alpha / 255 * Float32(rgba[0])
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avg_g += alpha / 255 * Float32(rgba[1])
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avg_b += alpha / 255 * Float32(rgba[2])
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avg_a += alpha
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rgba = rgba.advanced(by: 4)
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i += 1
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}
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}
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if avg_a > 0 {
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avg_r /= avg_a
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avg_g /= avg_a
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avg_b /= avg_a
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}
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let hasAlpha = avg_a < Float32(w * h)
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let l_limit = hasAlpha ? 5 : 7 // Use fewer luminance bits if there's alpha
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let imax_wh = max(w, h)
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let iwl_limit = l_limit * w
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let ihl_limit = l_limit * h
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let fmax_wh = Float32(imax_wh)
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let fwl_limit = Float32(iwl_limit)
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let fhl_limit = Float32(ihl_limit)
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let flx = round(fwl_limit / fmax_wh)
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let fly = round(fhl_limit / fmax_wh)
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var lx = Int(flx)
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var ly = Int(fly)
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lx = max(1, lx)
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ly = max(1, ly)
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var lpqa = [Float32](repeating: 0, count: w * h * 4)
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// Convert the image from RGBA to LPQA (composite atop the average color)
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rgba.withUnsafeBytes { rgba in
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lpqa.withUnsafeMutableBytes { lpqa in
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var rgba = rgba.baseAddress!.bindMemory(to: UInt8.self, capacity: rgba.count)
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var lpqa = lpqa.baseAddress!.bindMemory(to: Float32.self, capacity: lpqa.count)
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let n = w * h
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var i = 0
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while i < n {
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let alpha = Float32(rgba[3]) / 255
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let r = avg_r * (1 - alpha) + alpha / 255 * Float32(rgba[0])
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let g = avg_g * (1 - alpha) + alpha / 255 * Float32(rgba[1])
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let b = avg_b * (1 - alpha) + alpha / 255 * Float32(rgba[2])
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lpqa[0] = (r + g + b) / 3
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lpqa[1] = (r + g) / 2 - b
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lpqa[2] = r - g
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lpqa[3] = alpha
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rgba = rgba.advanced(by: 4)
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lpqa = lpqa.advanced(by: 4)
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i += 1
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}
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}
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}
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// Encode using the DCT into DC (constant) and normalized AC (varying) terms
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let encodeChannel = { (channel: UnsafePointer<Float32>, nx: Int, ny: Int) -> (Float32, [Float32], Float32) in
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var dc: Float32 = 0
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var ac: [Float32] = []
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var scale: Float32 = 0
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var fx = [Float32](repeating: 0, count: w)
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fx.withUnsafeMutableBytes { fx in
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let fx = fx.baseAddress!.bindMemory(to: Float32.self, capacity: fx.count)
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var cy = 0
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while cy < ny {
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var cx = 0
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while cx * ny < nx * (ny - cy) {
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var ptr = channel
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var f: Float32 = 0
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var x = 0
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while x < w {
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let fw = Float32(w)
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let fxx = Float32(x)
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let fcx = Float32(cx)
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fx[x] = cos(Float32.pi / fw * fcx * (fxx + 0.5))
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x += 1
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}
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var y = 0
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while y < h {
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let fh = Float32(h)
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let fyy = Float32(y)
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let fcy = Float32(cy)
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let fy = cos(Float32.pi / fh * fcy * (fyy + 0.5))
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var x = 0
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while x < w {
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f += ptr.pointee * fx[x] * fy
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x += 1
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ptr = ptr.advanced(by: 4)
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}
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y += 1
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}
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f /= Float32(w * h)
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if cx > 0 || cy > 0 {
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ac.append(f)
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scale = max(scale, abs(f))
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} else {
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dc = f
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}
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cx += 1
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}
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cy += 1
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}
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}
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if scale > 0 {
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let n = ac.count
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var i = 0
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while i < n {
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ac[i] = 0.5 + 0.5 / scale * ac[i]
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i += 1
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}
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}
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return (dc, ac, scale)
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}
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let (
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(l_dc, l_ac, l_scale),
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(p_dc, p_ac, p_scale),
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(q_dc, q_ac, q_scale),
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(a_dc, a_ac, a_scale)
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) = lpqa.withUnsafeBytes { lpqa in
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let lpqa = lpqa.baseAddress!.bindMemory(to: Float32.self, capacity: lpqa.count)
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return (
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encodeChannel(lpqa, max(3, lx), max(3, ly)),
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encodeChannel(lpqa.advanced(by: 1), 3, 3),
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encodeChannel(lpqa.advanced(by: 2), 3, 3),
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hasAlpha ? encodeChannel(lpqa.advanced(by: 3), 5, 5) : (1, [], 1)
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)
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}
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// Write the constants
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let isLandscape = w > h
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let fl_dc = round(63.0 * l_dc)
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let fp_dc = round(31.5 + 31.5 * p_dc)
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let fq_dc = round(31.5 + 31.5 * q_dc)
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let fl_scale = round(31.0 * l_scale)
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let il_dc = UInt32(fl_dc)
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let ip_dc = UInt32(fp_dc)
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let iq_dc = UInt32(fq_dc)
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let il_scale = UInt32(fl_scale)
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let ihasAlpha = UInt32(hasAlpha ? 1 : 0)
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let header24 = il_dc | (ip_dc << 6) | (iq_dc << 12) | (il_scale << 18) | (ihasAlpha << 23)
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let fp_scale = round(63.0 * p_scale)
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let fq_scale = round(63.0 * q_scale)
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let ilxy = UInt16(isLandscape ? ly : lx)
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let ip_scale = UInt16(fp_scale)
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let iq_scale = UInt16(fq_scale)
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let iisLandscape = UInt16(isLandscape ? 1 : 0)
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let header16 = ilxy | (ip_scale << 3) | (iq_scale << 9) | (iisLandscape << 15)
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var hash = Data(capacity: 25)
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hash.append(UInt8(header24 & 255))
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hash.append(UInt8((header24 >> 8) & 255))
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hash.append(UInt8(header24 >> 16))
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hash.append(UInt8(header16 & 255))
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hash.append(UInt8(header16 >> 8))
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var isOdd = false
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if hasAlpha {
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let fa_dc = round(15.0 * a_dc)
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let fa_scale = round(15.0 * a_scale)
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let ia_dc = UInt8(fa_dc)
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let ia_scale = UInt8(fa_scale)
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hash.append(ia_dc | (ia_scale << 4))
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}
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// Write the varying factors
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for ac in [l_ac, p_ac, q_ac] {
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for f in ac {
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let f15 = round(15.0 * f)
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let i15 = UInt8(f15)
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if isOdd {
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hash[hash.count - 1] |= i15 << 4
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} else {
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hash.append(i15)
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}
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isOdd = !isOdd
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}
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}
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if hasAlpha {
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for f in a_ac {
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let f15 = round(15.0 * f)
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let i15 = UInt8(f15)
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if isOdd {
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hash[hash.count - 1] |= i15 << 4
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} else {
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hash.append(i15)
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}
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isOdd = !isOdd
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}
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}
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return hash
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}
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func thumbHashToRGBA(hash: Data) -> (Int, Int, Data) {
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// Read the constants
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let h0 = UInt32(hash[0])
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let h1 = UInt32(hash[1])
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let h2 = UInt32(hash[2])
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let h3 = UInt16(hash[3])
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let h4 = UInt16(hash[4])
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let header24 = h0 | (h1 << 8) | (h2 << 16)
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let header16 = h3 | (h4 << 8)
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let il_dc = header24 & 63
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let ip_dc = (header24 >> 6) & 63
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let iq_dc = (header24 >> 12) & 63
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var l_dc = Float32(il_dc)
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var p_dc = Float32(ip_dc)
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var q_dc = Float32(iq_dc)
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l_dc = l_dc / 63
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p_dc = p_dc / 31.5 - 1
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q_dc = q_dc / 31.5 - 1
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let il_scale = (header24 >> 18) & 31
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var l_scale = Float32(il_scale)
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l_scale = l_scale / 31
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let hasAlpha = (header24 >> 23) != 0
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let ip_scale = (header16 >> 3) & 63
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let iq_scale = (header16 >> 9) & 63
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var p_scale = Float32(ip_scale)
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var q_scale = Float32(iq_scale)
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p_scale = p_scale / 63
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q_scale = q_scale / 63
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let isLandscape = (header16 >> 15) != 0
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let lx16 = max(3, isLandscape ? hasAlpha ? 5 : 7 : header16 & 7)
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let ly16 = max(3, isLandscape ? header16 & 7 : hasAlpha ? 5 : 7)
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let lx = Int(lx16)
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let ly = Int(ly16)
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var a_dc = Float32(1)
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var a_scale = Float32(1)
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if hasAlpha {
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let ia_dc = hash[5] & 15
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let ia_scale = hash[5] >> 4
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a_dc = Float32(ia_dc)
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a_scale = Float32(ia_scale)
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a_dc /= 15
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a_scale /= 15
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}
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// Read the varying factors (boost saturation by 1.25x to compensate for quantization)
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let ac_start = hasAlpha ? 6 : 5
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var ac_index = 0
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let decodeChannel = { (nx: Int, ny: Int, scale: Float32) -> [Float32] in
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var ac: [Float32] = []
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for cy in 0 ..< ny {
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var cx = cy > 0 ? 0 : 1
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while cx * ny < nx * (ny - cy) {
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let iac = (hash[ac_start + (ac_index >> 1)] >> ((ac_index & 1) << 2)) & 15
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var fac = Float32(iac)
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fac = (fac / 7.5 - 1) * scale
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ac.append(fac)
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ac_index += 1
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cx += 1
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}
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}
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return ac
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}
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let l_ac = decodeChannel(lx, ly, l_scale)
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let p_ac = decodeChannel(3, 3, p_scale * 1.25)
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let q_ac = decodeChannel(3, 3, q_scale * 1.25)
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let a_ac = hasAlpha ? decodeChannel(5, 5, a_scale) : []
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// Decode using the DCT into RGB
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let ratio = thumbHashToApproximateAspectRatio(hash: hash)
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let fw = round(ratio > 1 ? 32 : 32 * ratio)
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let fh = round(ratio > 1 ? 32 / ratio : 32)
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let w = Int(fw)
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let h = Int(fh)
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var rgba = Data(count: w * h * 4)
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let cx_stop = max(lx, hasAlpha ? 5 : 3)
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let cy_stop = max(ly, hasAlpha ? 5 : 3)
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var fx = [Float32](repeating: 0, count: cx_stop)
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var fy = [Float32](repeating: 0, count: cy_stop)
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fx.withUnsafeMutableBytes { fx in
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let fx = fx.baseAddress!.bindMemory(to: Float32.self, capacity: fx.count)
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fy.withUnsafeMutableBytes { fy in
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let fy = fy.baseAddress!.bindMemory(to: Float32.self, capacity: fy.count)
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rgba.withUnsafeMutableBytes { rgba in
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var rgba = rgba.baseAddress!.bindMemory(to: UInt8.self, capacity: rgba.count)
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var y = 0
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while y < h {
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var x = 0
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while x < w {
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var l = l_dc
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var p = p_dc
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var q = q_dc
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var a = a_dc
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// Precompute the coefficients
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var cx = 0
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while cx < cx_stop {
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let fw = Float32(w)
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let fxx = Float32(x)
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let fcx = Float32(cx)
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fx[cx] = cos(Float32.pi / fw * (fxx + 0.5) * fcx)
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cx += 1
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}
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var cy = 0
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while cy < cy_stop {
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let fh = Float32(h)
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let fyy = Float32(y)
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let fcy = Float32(cy)
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fy[cy] = cos(Float32.pi / fh * (fyy + 0.5) * fcy)
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cy += 1
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}
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// Decode L
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var j = 0
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cy = 0
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while cy < ly {
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var cx = cy > 0 ? 0 : 1
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let fy2 = fy[cy] * 2
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while cx * ly < lx * (ly - cy) {
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l += l_ac[j] * fx[cx] * fy2
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j += 1
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cx += 1
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}
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cy += 1
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}
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// Decode P and Q
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j = 0
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cy = 0
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while cy < 3 {
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var cx = cy > 0 ? 0 : 1
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let fy2 = fy[cy] * 2
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while cx < 3 - cy {
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let f = fx[cx] * fy2
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p += p_ac[j] * f
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q += q_ac[j] * f
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j += 1
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cx += 1
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}
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cy += 1
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}
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// Decode A
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if hasAlpha {
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j = 0
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cy = 0
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while cy < 5 {
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var cx = cy > 0 ? 0 : 1
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let fy2 = fy[cy] * 2
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while cx < 5 - cy {
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a += a_ac[j] * fx[cx] * fy2
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j += 1
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cx += 1
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}
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cy += 1
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}
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}
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// Convert to RGB
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var b = l - 2 / 3 * p
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var r = (3 * l - b + q) / 2
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var g = r - q
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r = max(0, 255 * min(1, r))
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g = max(0, 255 * min(1, g))
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b = max(0, 255 * min(1, b))
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a = max(0, 255 * min(1, a))
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rgba[0] = UInt8(r)
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rgba[1] = UInt8(g)
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rgba[2] = UInt8(b)
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rgba[3] = UInt8(a)
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rgba = rgba.advanced(by: 4)
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x += 1
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}
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y += 1
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}
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}
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}
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}
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return (w, h, rgba)
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}
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func thumbHashToAverageRGBA(hash: Data) -> (Float32, Float32, Float32, Float32) {
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let h0 = UInt32(hash[0])
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let h1 = UInt32(hash[1])
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let h2 = UInt32(hash[2])
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let header = h0 | (h1 << 8) | (h2 << 16)
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let il = header & 63
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let ip = (header >> 6) & 63
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let iq = (header >> 12) & 63
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var l = Float32(il)
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var p = Float32(ip)
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var q = Float32(iq)
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l = l / 63
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p = p / 31.5 - 1
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q = q / 31.5 - 1
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let hasAlpha = (header >> 23) != 0
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var a = Float32(1)
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if hasAlpha {
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let ia = hash[5] & 15
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a = Float32(ia)
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a = a / 15
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}
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let b = l - 2 / 3 * p
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let r = (3 * l - b + q) / 2
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let g = r - q
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return (
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max(0, min(1, r)),
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max(0, min(1, g)),
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max(0, min(1, b)),
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a
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)
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}
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func thumbHashToApproximateAspectRatio(hash: Data) -> Float32 {
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let header = hash[3]
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let hasAlpha = (hash[2] & 0x80) != 0
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let isLandscape = (hash[4] & 0x80) != 0
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let lx = isLandscape ? hasAlpha ? 5 : 7 : header & 7
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let ly = isLandscape ? header & 7 : hasAlpha ? 5 : 7
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return Float32(lx) / Float32(ly)
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}
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#if os(iOS) || os(tvOS)
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import UIKit
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func thumbHash(fromImage: UIImage) -> Data {
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let size = fromImage.size
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let w = Int(round(100 * size.width / max(size.width, size.height)))
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let h = Int(round(100 * size.height / max(size.width, size.height)))
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var rgba = Data(count: w * h * 4)
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rgba.withUnsafeMutableBytes { rgba in
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if
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let space = fromImage.cgImage?.colorSpace,
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let context = CGContext(
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data: rgba.baseAddress,
|
|
width: w,
|
|
height: h,
|
|
bitsPerComponent: 8,
|
|
bytesPerRow: w * 4,
|
|
space: space,
|
|
bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue
|
|
)
|
|
{
|
|
// EXIF orientation only works if you draw the UIImage, not the CGImage
|
|
context.concatenate(CGAffineTransform(1, 0, 0, -1, 0, CGFloat(h)))
|
|
UIGraphicsPushContext(context)
|
|
fromImage.draw(in: CGRect(x: 0, y: 0, width: w, height: h))
|
|
UIGraphicsPopContext()
|
|
|
|
// Convert from premultiplied alpha to unpremultiplied alpha
|
|
var rgba = rgba.baseAddress!.bindMemory(to: UInt8.self, capacity: rgba.count)
|
|
let n = w * h
|
|
var i = 0
|
|
while i < n {
|
|
let a = UInt16(rgba[3])
|
|
if a > 0 && a < 255 {
|
|
var r = UInt16(rgba[0])
|
|
var g = UInt16(rgba[1])
|
|
var b = UInt16(rgba[2])
|
|
r = min(255, r * 255 / a)
|
|
g = min(255, g * 255 / a)
|
|
b = min(255, b * 255 / a)
|
|
rgba[0] = UInt8(r)
|
|
rgba[1] = UInt8(g)
|
|
rgba[2] = UInt8(b)
|
|
}
|
|
rgba = rgba.advanced(by: 4)
|
|
i += 1
|
|
}
|
|
}
|
|
}
|
|
return rgbaToThumbHash(w: w, h: h, rgba: rgba)
|
|
}
|
|
|
|
func image(fromThumbhash: Data) -> UIImage {
|
|
var (w, h, rgba) = thumbHashToRGBA(hash: fromThumbhash)
|
|
rgba.withUnsafeMutableBytes { rgba in
|
|
// Convert from unpremultiplied alpha to premultiplied alpha
|
|
var rgba = rgba.baseAddress!.bindMemory(to: UInt8.self, capacity: rgba.count)
|
|
let n = w * h
|
|
var i = 0
|
|
while i < n {
|
|
let a = UInt16(rgba[3])
|
|
if a < 255 {
|
|
var r = UInt16(rgba[0])
|
|
var g = UInt16(rgba[1])
|
|
var b = UInt16(rgba[2])
|
|
r = min(255, r * a / 255)
|
|
g = min(255, g * a / 255)
|
|
b = min(255, b * a / 255)
|
|
rgba[0] = UInt8(r)
|
|
rgba[1] = UInt8(g)
|
|
rgba[2] = UInt8(b)
|
|
}
|
|
rgba = rgba.advanced(by: 4)
|
|
i += 1
|
|
}
|
|
}
|
|
let image = CGImage(
|
|
width: w,
|
|
height: h,
|
|
bitsPerComponent: 8,
|
|
bitsPerPixel: 32,
|
|
bytesPerRow: w * 4,
|
|
space: CGColorSpaceCreateDeviceRGB(),
|
|
bitmapInfo: CGBitmapInfo(rawValue: CGBitmapInfo.byteOrder32Big.rawValue | CGImageAlphaInfo.premultipliedLast.rawValue),
|
|
provider: CGDataProvider(data: rgba as CFData)!,
|
|
decode: nil,
|
|
shouldInterpolate: true,
|
|
intent: .perceptual
|
|
)
|
|
return UIImage(cgImage: image!)
|
|
}
|
|
#endif
|