mirror of
https://github.com/simplex-chat/simplex-chat.git
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88 lines
3.8 KiB
Swift
88 lines
3.8 KiB
Swift
// Makes a group avatar the way the app makes profile images (resizeImageToStrSize in apps/ios/SimpleXChat/ImageUtils.swift):
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// a JPEG at quality 0.85 drawn at scale 1, shrunk by sqrt(size / 12500), at most halved per step,
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// until its data URI is at most 12500 characters. The picture is synthetic and photo-like: a gradient,
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// discs and noise, with more noise for a higher detail.
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// Usage: avatar <seed> <detail 0...1> <output file> [side in pixels, default 1024]
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import CoreGraphics
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import Foundation
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import ImageIO
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let maxDataSize = 12500
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let colorSpace = CGColorSpace(name: CGColorSpace.sRGB)!
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struct Random {
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var state: UInt64
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mutating func next() -> Double {
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state = state &* 6364136223846793005 &+ 1442695040888963407
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return Double(state >> 11) / Double(UInt64(1) << 53)
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}
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mutating func color(alpha: Double = 1) -> CGColor {
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let components: [CGFloat] = [next(), next(), next(), alpha]
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return CGColor(colorSpace: colorSpace, components: components)!
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}
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}
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func context(_ width: Int, _ height: Int) -> CGContext {
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CGContext(data: nil, width: width, height: height, bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: CGImageAlphaInfo.noneSkipLast.rawValue)!
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}
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func picture(side: Int, detail: Double, random: inout Random) -> CGImage {
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let ctx = context(side, side)
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let gradient = CGGradient(colorsSpace: colorSpace, colors: [random.color(), random.color()] as CFArray, locations: [0, 1])!
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ctx.drawLinearGradient(gradient, start: .zero, end: CGPoint(x: 0, y: side), options: [])
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for _ in 0..<24 {
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let r = Double(side) * (0.05 + 0.25 * random.next())
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let alpha = 0.4 + 0.5 * random.next()
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ctx.setFillColor(random.color(alpha: alpha))
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ctx.fillEllipse(in: CGRect(x: Double(side) * random.next() - r, y: Double(side) * random.next() - r, width: 2 * r, height: 2 * r))
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}
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let pixels = ctx.data!.bindMemory(to: UInt8.self, capacity: ctx.bytesPerRow * side)
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let amplitude = 96 * detail
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for y in 0..<side {
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for x in 0..<side {
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let i = y * ctx.bytesPerRow + x * 4
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for c in 0..<3 {
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let v = Double(pixels[i + c]) + amplitude * (random.next() - 0.5)
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pixels[i + c] = UInt8(max(0, min(255, v)))
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}
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}
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}
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return ctx.makeImage()!
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}
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func jpegDataURI(_ image: CGImage) -> String {
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let data = NSMutableData()
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let destination = CGImageDestinationCreateWithData(data as CFMutableData, "public.jpeg" as CFString, 1, nil)!
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CGImageDestinationAddImage(destination, image, [kCGImageDestinationLossyCompressionQuality: 0.85] as CFDictionary)
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CGImageDestinationFinalize(destination)
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return "data:image/jpg;base64," + (data as Data).base64EncodedString()
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}
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func reduced(_ image: CGImage, ratio: Double) -> CGImage {
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let width = Int(floor(Double(image.width) / ratio))
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let height = Int(floor(Double(image.height) / ratio))
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let ctx = context(width, height)
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ctx.draw(image, in: CGRect(x: 0, y: 0, width: width, height: height))
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return ctx.makeImage()!
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}
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let args = CommandLine.arguments
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guard args.count == 4 || args.count == 5, let seed = UInt64(args[1]), let detail = Double(args[2]), let side = Int(args.count == 5 ? args[4] : "1024") else {
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print("usage: avatar <seed> <detail 0...1> <output file> [side in pixels, default 1024]")
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exit(1)
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}
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var generator = Random(state: seed)
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var image = picture(side: side, detail: detail, random: &generator)
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var uri = jpegDataURI(image)
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var steps = 0
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while uri.count > maxDataSize {
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image = reduced(image, ratio: min((Double(uri.count) / Double(maxDataSize)).squareRoot(), 2))
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uri = jpegDataURI(image)
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steps += 1
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}
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try uri.write(toFile: args[3], atomically: true, encoding: .utf8)
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print("\(args[3]): \(image.width)x\(image.height) px after \(steps) steps, \(uri.count) characters")
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