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diff --git a/native/expo-modules/thumbhash/ios/ThumbhashModule.swift b/native/expo-modules/thumbhash/ios/ThumbhashModule.swift
--- a/native/expo-modules/thumbhash/ios/ThumbhashModule.swift
+++ b/native/expo-modules/thumbhash/ios/ThumbhashModule.swift
@@ -4,8 +4,25 @@
public func definition() -> ModuleDefinition {
Name("Thumbhash")
- AsyncFunction("generateThumbHash") { () -> String in
- "unimplemented"
- }
+ AsyncFunction("generateThumbHash", generateThumbHash)
+ }
+}
+
+// MARK: - Function implementations
+
+private func generateThumbHash(photoURI: URL) throws -> String {
+ let imageData = try Data(contentsOf: photoURI)
+ guard let image = UIImage(data: imageData) else {
+ throw LoadingFailureException(photoURI.absoluteString)
+ }
+
+ return thumbHash(fromImage: image).base64EncodedString()
+}
+
+// MARK: - Exception definitions
+
+private class LoadingFailureException: GenericException<String> {
+ override var reason: String {
+ "Failed to load image URI: \(param)"
}
}
diff --git a/native/expo-modules/thumbhash/ios/third_party/LICENSE.txt b/native/expo-modules/thumbhash/ios/third_party/LICENSE.txt
new file mode 100644
--- /dev/null
+++ b/native/expo-modules/thumbhash/ios/third_party/LICENSE.txt
@@ -0,0 +1,19 @@
+Copyright (c) 2023 Evan Wallace
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/native/expo-modules/thumbhash/ios/third_party/Thumbhash.swift b/native/expo-modules/thumbhash/ios/third_party/Thumbhash.swift
new file mode 100644
--- /dev/null
+++ b/native/expo-modules/thumbhash/ios/third_party/Thumbhash.swift
@@ -0,0 +1,294 @@
+import Foundation
+import UIKit
+
+// Thumbhash implementation thanks to @evanw work
+// https://github.com/evanw/thumbhash
+// NOTE: Swift has an exponential-time type checker and compiling very simple
+// expressions can easily take many seconds, especially when expressions involve
+// numeric type constructors.
+//
+// This file deliberately breaks compound expressions up into separate variables
+// to improve compile time even though this comes at the expense of readability.
+// This is a known workaround for this deficiency in the Swift compiler.
+//
+// The following command is helpful when debugging Swift compile time issues:
+//
+// swiftc ThumbHash.swift -Xfrontend -debug-time-function-bodies
+//
+// These optimizations brought the compile time for this file from around 2.5
+// seconds to around 250ms (10x faster).
+// NOTE: Swift's debug-build performance of for-in loops over numeric ranges is
+// really awful. Debug builds compile a very generic indexing iterator thing
+// that makes many nested calls for every iteration, which makes debug-build
+// performance crawl.
+//
+// This file deliberately avoids for-in loops that loop for more than a few
+// times to improve debug-build run time even though this comes at the expense
+// of readability. Similarly unsafe pointers are used instead of array getters
+// to avoid unnecessary bounds checks, which have extra overhead in debug builds
+//
+// These optimizations brought the run time to encode and decode 10 ThumbHashes
+// in debug mode from 700ms to 70ms (10x faster).
+// swiftlint:disable all
+private func rgbaToThumbHash(w: Int, h: Int, rgba: Data) -> Data {
+ // Encoding an image larger than 100x100 is slow with no benefit
+ assert(w <= 100 && h <= 100)
+ assert(rgba.count == w * h * 4)
+
+ // Determine the average color
+ var avg_r: Float32 = 0
+ var avg_g: Float32 = 0
+ var avg_b: Float32 = 0
+ var avg_a: Float32 = 0
+ rgba.withUnsafeBytes { rgba in
+ var rgba = rgba.baseAddress!.bindMemory(to: UInt8.self,
+ capacity: rgba.count)
+ let n = w * h
+ var i = 0
+ while i < n {
+ let alpha = Float32(rgba[3]) / 255
+ avg_r += alpha / 255 * Float32(rgba[0])
+ avg_g += alpha / 255 * Float32(rgba[1])
+ avg_b += alpha / 255 * Float32(rgba[2])
+ avg_a += alpha
+ rgba = rgba.advanced(by: 4)
+ i += 1
+ }
+ }
+ if avg_a > 0 {
+ avg_r /= avg_a
+ avg_g /= avg_a
+ avg_b /= avg_a
+ }
+
+ let hasAlpha = avg_a < Float32(w * h)
+ let l_limit = hasAlpha ? 5 : 7 // Use fewer luminance bits if there's alpha
+ let imax_wh = max(w, h)
+ let iwl_limit = l_limit * w
+ let ihl_limit = l_limit * h
+ let fmax_wh = Float32(imax_wh)
+ let fwl_limit = Float32(iwl_limit)
+ let fhl_limit = Float32(ihl_limit)
+ let flx = round(fwl_limit / fmax_wh)
+ let fly = round(fhl_limit / fmax_wh)
+ var lx = Int(flx)
+ var ly = Int(fly)
+ lx = max(1, lx)
+ ly = max(1, ly)
+ var lpqa = [Float32](repeating: 0, count: w * h * 4)
+
+ // Convert the image from RGBA to LPQA (composite atop the average color)
+ rgba.withUnsafeBytes { rgba in
+ lpqa.withUnsafeMutableBytes { lpqa in
+ var rgba = rgba.baseAddress!.bindMemory(to: UInt8.self,
+ capacity: rgba.count)
+ var lpqa = lpqa.baseAddress!.bindMemory(to: Float32.self,
+ capacity: lpqa.count)
+ let n = w * h
+ var i = 0
+ while i < n {
+ let alpha = Float32(rgba[3]) / 255
+ let r = avg_r * (1 - alpha) + alpha / 255 * Float32(rgba[0])
+ let g = avg_g * (1 - alpha) + alpha / 255 * Float32(rgba[1])
+ let b = avg_b * (1 - alpha) + alpha / 255 * Float32(rgba[2])
+ lpqa[0] = (r + g + b) / 3
+ lpqa[1] = (r + g) / 2 - b
+ lpqa[2] = r - g
+ lpqa[3] = alpha
+ rgba = rgba.advanced(by: 4)
+ lpqa = lpqa.advanced(by: 4)
+ i += 1
+ }
+ }
+ }
+
+ // Encode using the DCT into DC (constant) and normalized AC (varying) terms
+ let encodeChannel = { (channel: UnsafePointer<Float32>, nx: Int, ny: Int) ->
+ (Float32, [Float32], Float32) in
+ var dc: Float32 = 0
+ var ac: [Float32] = []
+ var scale: Float32 = 0
+ var fx = [Float32](repeating: 0, count: w)
+ fx.withUnsafeMutableBytes { fx in
+ let fx = fx.baseAddress!.bindMemory(to: Float32.self, capacity: fx.count)
+ var cy = 0
+ while cy < ny {
+ var cx = 0
+ while cx * ny < nx * (ny - cy) {
+ var ptr = channel
+ var f: Float32 = 0
+ var x = 0
+ while x < w {
+ let fw = Float32(w)
+ let fxx = Float32(x)
+ let fcx = Float32(cx)
+ fx[x] = cos(Float32.pi / fw * fcx * (fxx + 0.5))
+ x += 1
+ }
+ var y = 0
+ while y < h {
+ let fh = Float32(h)
+ let fyy = Float32(y)
+ let fcy = Float32(cy)
+ let fy = cos(Float32.pi / fh * fcy * (fyy + 0.5))
+ var x = 0
+ while x < w {
+ f += ptr.pointee * fx[x] * fy
+ x += 1
+ ptr = ptr.advanced(by: 4)
+ }
+ y += 1
+ }
+ f /= Float32(w * h)
+ if cx > 0 || cy > 0 {
+ ac.append(f)
+ scale = max(scale, abs(f))
+ } else {
+ dc = f
+ }
+ cx += 1
+ }
+ cy += 1
+ }
+ }
+ if scale > 0 {
+ let n = ac.count
+ var i = 0
+ while i < n {
+ ac[i] = 0.5 + 0.5 / scale * ac[i]
+ i += 1
+ }
+ }
+ return (dc, ac, scale)
+ }
+ let (
+ (l_dc, l_ac, l_scale),
+ (p_dc, p_ac, p_scale),
+ (q_dc, q_ac, q_scale),
+ (a_dc, a_ac, a_scale)
+ ) = lpqa.withUnsafeBytes { lpqa in
+ let lpqa = lpqa.baseAddress!.bindMemory(to: Float32.self,
+ capacity: lpqa.count)
+ return (
+ encodeChannel(lpqa, max(3, lx), max(3, ly)),
+ encodeChannel(lpqa.advanced(by: 1), 3, 3),
+ encodeChannel(lpqa.advanced(by: 2), 3, 3),
+ hasAlpha ? encodeChannel(lpqa.advanced(by: 3), 5, 5) : (1, [], 1)
+ )
+ }
+
+ // Write the constants
+ let isLandscape = w > h
+ let fl_dc = round(63.0 * l_dc)
+ let fp_dc = round(31.5 + 31.5 * p_dc)
+ let fq_dc = round(31.5 + 31.5 * q_dc)
+ let fl_scale = round(31.0 * l_scale)
+ let il_dc = UInt32(fl_dc)
+ let ip_dc = UInt32(fp_dc)
+ let iq_dc = UInt32(fq_dc)
+ let il_scale = UInt32(fl_scale)
+ let ihasAlpha = UInt32(hasAlpha ? 1 : 0)
+ let header24 = il_dc
+ | (ip_dc << 6)
+ | (iq_dc << 12)
+ | (il_scale << 18)
+ | (ihasAlpha << 23)
+ let fp_scale = round(63.0 * p_scale)
+ let fq_scale = round(63.0 * q_scale)
+ let ilxy = UInt16(isLandscape ? ly : lx)
+ let ip_scale = UInt16(fp_scale)
+ let iq_scale = UInt16(fq_scale)
+ let iisLandscape = UInt16(isLandscape ? 1 : 0)
+ let header16 = ilxy | (ip_scale << 3) | (iq_scale << 9) | (iisLandscape << 15)
+ var hash = Data(capacity: 25)
+ hash.append(UInt8(header24 & 255))
+ hash.append(UInt8((header24 >> 8) & 255))
+ hash.append(UInt8(header24 >> 16))
+ hash.append(UInt8(header16 & 255))
+ hash.append(UInt8(header16 >> 8))
+ var isOdd = false
+ if hasAlpha {
+ let fa_dc = round(15.0 * a_dc)
+ let fa_scale = round(15.0 * a_scale)
+ let ia_dc = UInt8(fa_dc)
+ let ia_scale = UInt8(fa_scale)
+ hash.append(ia_dc | (ia_scale << 4))
+ }
+
+ // Write the varying factors
+ for ac in [l_ac, p_ac, q_ac] {
+ for f in ac {
+ let f15 = round(15.0 * f)
+ let i15 = UInt8(f15)
+ if isOdd {
+ hash[hash.count - 1] |= i15 << 4
+ } else {
+ hash.append(i15)
+ }
+ isOdd = !isOdd
+ }
+ }
+ if hasAlpha {
+ for f in a_ac {
+ let f15 = round(15.0 * f)
+ let i15 = UInt8(f15)
+ if isOdd {
+ hash[hash.count - 1] |= i15 << 4
+ } else {
+ hash.append(i15)
+ }
+ isOdd = !isOdd
+ }
+ }
+ return hash
+}
+
+func thumbHash(fromImage: UIImage) -> Data {
+ let size = fromImage.size
+ let w = Int(round(100 * size.width / max(size.width, size.height)))
+ let h = Int(round(100 * size.height / max(size.width, size.height)))
+ var rgba = Data(count: w * h * 4)
+ rgba.withUnsafeMutableBytes { rgba in
+ if
+ let space = fromImage.cgImage?.colorSpace,
+ let context = CGContext(
+ 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)
+}

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