dither4/dither-image.js

import {
    writeFileSync
} from 'fs';

import Jimp from 'Jimp';


function repeat(val, n) {
    let arr = [];
    for (let i = 0; i < n; i++) {
        arr.push(val);
    }
    return arr;
}

function zeroes(n) {
    return repeat(0, n);
}

function toLinear(val) {
    // use a 2.4 gamma approximation
    // this is BT.1886 compatible
    // and simpler than sRGB
    let unit = val / 255;
    unit **= 2.4;
    return unit * 255;
}

function fromLinear(val) {
    let unit = val / 255;
    unit **= (1 / 2.4);
    return unit * 255;
}

function fromSRGB(val) {
    val /= 255;
    if (val <= 0.04045) {
        val /= 12.92;
    } else {
        val = ((val + 0.055) / 1.055) ** 2.4;
    }
    val *= 255;
    return val;
}

function toSRGB(val) {
    val /= 255;
    if (val <= 0.0031308) {
        val *= 12.92;
    } else {
        val = (val * 1.055) ** (1.0 / 2.4) - 0.055;
    }
    val *= 255;
    return val;
}

class RGB {
    constructor(r, g, b) {
        this.r = r;
        this.g = g;
        this.b = b;
    }

    clone() {
        return new RGB(this.r, this.g, this.b);
    }

    static fromHex(val) {
        let r = (val >>> 16) & 0xff;
        let g = (val >>> 8) & 0xff;
        let b = val & 0xff;
        return new RGB(r,g,b);
    }

    static fromGTIA(val) {
        // This seems off from what Atari800 does
        // https://forums.atariage.com/topic/107853-need-the-256-colors/page/2/#comment-1312467
        let cr = (val >> 4) & 15;
        let lm = val & 15;
        let crlv = cr ? 50 : 0;

        /*
        let phase = ((cr - 1) * 25 - 58) * (2 * Math.PI / 360);

        let y = 255 * (lm + 1) / 16;
        let i = crlv * Math.cos(phase);
        let q = crlv * Math.sin(phase);

        let r = y + 0.956 * i + 0.621 * q;
        let g = y - 0.272 * i - 0.647 * q;
        let b = y - 1.107 * i + 1.704 * q;
        */

        // PAL
        let phase = ((cr - 1) * 25.7 - 15) * (2 * Math.PI / 360);

        let y = 255 * (lm + 1) / 16;
        let i = crlv * Math.cos(phase);
        let q = crlv * Math.sin(phase);

        let r = y + 0.956 * i + 0.621 * q;
        let g = y - 0.272 * i - 0.647 * q;
        let b = y - 1.107 * i + 1.704 * q;

        return new RGB(r, g, b).clamp().fromSRGB();
    }

    map(callback) {
        return new RGB(
            callback(this.r),
            callback(this.g),
            callback(this.b)
        );
    }

    fromNTSC() {
        return this.map(toLinear);
    }

    toNTSC() {
        return this.map(fromLinear);
    }

    fromSRGB() {
        return this.map(fromSRGB);
    }

    toSRGB() {
        return this.map(toSRGB);
    }

    clamp() {
        return this.map((val) => {
            if (val < 0) return 0;
            if (val > 255) return 255;
            return val;
        });
    }

    inc(other) {
        this.r += other.r;
        this.g += other.g;
        this.b += other.b;
        return this;
    }

    add(other) {
        return new RGB(
            this.r + other.r,
            this.g + other.g,
            this.b + other.b
        );
    }

    difference(other) {
        return new RGB(
            this.r - other.r,
            this.g - other.g,
            this.b - other.b
        );
    }

    multiply(scalar) {
        return new RGB(
            this.r * scalar,
            this.g * scalar,
            this.b * scalar,
        );
    }

    divide(scalar) {
        return new RGB(
            this.r / scalar,
            this.g / scalar,
            this.b / scalar,
        );
    }

    magnitude() {
        return Math.sqrt(this.magnitude2());
    }

    magnitude2() {
        return this.r * this.r +
            this.g * this.g +
            this.b * this.b;
    }

    sum() {
        return this.r + this.g + this.b;
    }

    lumaScale() {
        return new RGB(
            this.r * 0.299,
            this.g * 0.586,
            this.b * 0.114
        );
    }

    luma() {
        return this.lumaScale().sum();
    }
}

/*
// snarfed from https://lospec.com/palette-list/atari-8-bit-family-gtia
// which was calculated with Retrospecs App's Atari 800 emulator
let atariRGB = [
    0x000000,
    0x111111,
    0x222222,
    0x333333,
    0x444444,
    0x555555,
    0x666666,
    0x777777,
    0x888888,
    0x999999,
    0xaaaaaa,
    0xbbbbbb,
    0xcccccc,
    0xdddddd,
    0xeeeeee,
    0xffffff,
    0x190700,
    0x2a1800,
    0x3b2900,
    0x4c3a00,
    0x5d4b00,
    0x6e5c00,
    0x7f6d00,
    0x907e09,
    0xa18f1a,
    0xb3a02b,
    0xc3b13c,
    0xd4c24d,
    0xe5d35e,
    0xf7e46f,
    0xfff582,
    0xffff96,
    0x310000,
    0x3f0000,
    0x531700,
    0x642800,
    0x753900,
    0x864a00,
    0x975b0a,
    0xa86c1b,
    0xb97d2c,
    0xca8e3d,
    0xdb9f4e,
    0xecb05f,
    0xfdc170,
    0xffd285,
    0xffe39c,
    0xfff4b2,
    0x420404,
    0x4f0000,
    0x600800,
    0x711900,
    0x822a0d,
    0x933b1e,
    0xa44c2f,
    0xb55d40,
    0xc66e51,
    0xd77f62,
    0xe89073,
    0xf9a183,
    0xffb298,
    0xffc3ae,
    0xffd4c4,
    0xffe5da,
    0x410103,
    0x50000f,
    0x61001b,
    0x720f2b,
    0x83203c,
    0x94314d,
    0xa5425e,
    0xb6536f,
    0xc76480,
    0xd87591,
    0xe986a2,
    0xfa97b3,
    0xffa8c8,
    0xffb9de,
    0xffcaef,
    0xfbdcf6,
    0x330035,
    0x440041,
    0x55004c,
    0x660c5c,
    0x771d6d,
    0x882e7e,
    0x993f8f,
    0xaa50a0,
    0xbb61b1,
    0xcc72c2,
    0xdd83d3,
    0xee94e4,
    0xffa5e4,
    0xffb6e9,
    0xffc7ee,
    0xffd8f3,
    0x1d005c,
    0x2e0068,
    0x400074,
    0x511084,
    0x622195,
    0x7332a6,
    0x8443b7,
    0x9554c8,
    0xa665d9,
    0xb776ea,
    0xc887eb,
    0xd998eb,
    0xe9a9ec,
    0xfbbaeb,
    0xffcbef,
    0xffdff9,
    0x020071,
    0x13007d,
    0x240b8c,
    0x351c9d,
    0x462dae,
    0x573ebf,
    0x684fd0,
    0x7960e1,
    0x8a71f2,
    0x9b82f7,
    0xac93f7,
    0xbda4f7,
    0xceb5f7,
    0xdfc6f7,
    0xf0d7f7,
    0xffe8f8,
    0x000068,
    0x000a7c,
    0x081b90,
    0x192ca1,
    0x2a3db2,
    0x3b4ec3,
    0x4c5fd4,
    0x5d70e5,
    0x6e81f6,
    0x7f92ff,
    0x90a3ff,
    0xa1b4ff,
    0xb2c5ff,
    0xc3d6ff,
    0xd4e7ff,
    0xe5f8ff,
    0x000a4d,
    0x001b63,
    0x002c79,
    0x023d8f,
    0x134ea0,
    0x245fb1,
    0x3570c2,
    0x4681d3,
    0x5792e4,
    0x68a3f5,
    0x79b4ff,
    0x8ac5ff,
    0x9bd6ff,
    0xace7ff,
    0xbdf8ff,
    0xceffff,
    0x001a26,
    0x002b3c,
    0x003c52,
    0x004d68,
    0x065e7c,
    0x176f8d,
    0x28809e,
    0x3991af,
    0x4aa2c0,
    0x5bb3d1,
    0x6cc4e2,
    0x7dd5f3,
    0x8ee6ff,
    0x9ff7ff,
    0xb0ffff,
    0xc1ffff,
    0x01250a,
    0x023610,
    0x004622,
    0x005738,
    0x05684d,
    0x16795e,
    0x278a6f,
    0x389b80,
    0x49ac91,
    0x5abda2,
    0x6bceb3,
    0x7cdfc4,
    0x8df0d5,
    0x9effe5,
    0xaffff1,
    0xc0fffd,
    0x04260d,
    0x043811,
    0x054713,
    0x005a1b,
    0x106b1b,
    0x217c2c,
    0x328d3d,
    0x439e4e,
    0x54af5f,
    0x65c070,
    0x76d181,
    0x87e292,
    0x98f3a3,
    0xa9ffb3,
    0xbaffbf,
    0xcbffcb,
    0x00230a,
    0x003510,
    0x044613,
    0x155613,
    0x266713,
    0x377813,
    0x488914,
    0x599a25,
    0x6aab36,
    0x7bbc47,
    0x8ccd58,
    0x9dde69,
    0xaeef7a,
    0xbfff8b,
    0xd0ff97,
    0xe1ffa3,
    0x001707,
    0x0e2808,
    0x1f3908,
    0x304a08,
    0x415b08,
    0x526c08,
    0x637d08,
    0x748e0d,
    0x859f1e,
    0x96b02f,
    0xa7c140,
    0xb8d251,
    0xc9e362,
    0xdaf473,
    0xebff82,
    0xfcff8e,
    0x1b0701,
    0x2c1801,
    0x3c2900,
    0x4d3b00,
    0x5f4c00,
    0x705e00,
    0x816f00,
    0x938009,
    0xa4921a,
    0xb2a02b,
    0xc7b43d,
    0xd8c64e,
    0xead760,
    0xf6e46f,
    0xfffa84,
    0xffff99,
].map((hex) => RGB.fromHex(hex).fromNTSC());
//].map((hex) => RGB.fromHex(hex));
*/

let atariRGB = [];
for (let i = 0; i < 256; i++) {
    atariRGB[i] = RGB.fromGTIA(i);
}



/**
 * Dither RGB input data with a target palette size.
 * If the number of used colors exceeds `n`, the
 * palette will be reduced until it fits.
 * @param {RGB[]} input source scanline data, in linear RGB
 * @param {number[]} palette - current working palette, as Atari 8-bit color values (low nybble luminance, high nybble hue)
 * @param {number} n - target color count
 * @param {number} y
 * @returns {{output: number[], palette: number[], error: RGB[]}}
 */
function decimate(input, palette, n) {

    let width = input.length;

    let inputPixel = (x, error) => {
        let rgb = input[x].clone();
        if (error) {
            rgb = rgb.add(error.cur[x]);
        }
        return rgb.clamp();
    };

    // Apply dithering with given palette and collect color usage stats
    let dither = (palette) => {
        let error = {
            cur: [],
            next: [],
        };
        for (let i = 0; i < width; i++) {
            error.cur[i] = new RGB(0, 0, 0);
            error.next[i] = new RGB(0, 0, 0);
        }

        let output = zeroes(width);
        let popularity = zeroes(palette.length);
        let distance2 = 0;

        let nextError = new RGB(0, 0, 0);

        // Try dithering with this palette.
        for (let x = 0; x < width; x++) {
            let rgb = inputPixel(x, error);

            // find the closest possible color
            // @todo consider doing the difference scoring in luminance and hue spaces
            let shortest = Infinity;
            let pick = 1;

            for (let i = 0; i < palette.length; i++) {
                let diff = rgb.difference(atariRGB[palette[i]]);
                let dist = diff.magnitude();
                if (dist < shortest) {
                    nextError = diff;
                    shortest = dist;
                    pick = i;
                }
            }

            output[x] = pick;
            popularity[pick]++;

            let share = (n) => nextError.multiply(n / 16);

            error.cur[x + 1]?.inc(share(7));
            error.next[x - 1]?.inc(share(3));
            error.next[x    ]?.inc(share(5));
            error.next[x + 1]?.inc(share(1));
        }
        return {
            output,
            palette,
            distance2,
            popularity,
            error: error.next
        };
    };


    let decimated = palette.slice();
    
    // force to grayscale
    //decimated = [0, 5, 10, 15];

    // force to rgb
    //decimated = [0, 0x36, 0xb6, 0x86];

    // force to rWb
    //decimated = [0, 0x36, 0x0f, 0x86];
    
    let reserved = [0]; // black
    //reserved = [0, 15]; // black, white
    //reserved = [0, 5, 10, 15]; // grayscale
    //reserved = [0, 0x48, 0x78, 15]; // vaporwave
    //reserved = [0, 0x3c, 0x78, 15]; // red/blue/white

    /*
    if (( y & 1 ) === 0) {
        reserved = [0, 0x3c, 0x1e, 15]; // red/yellow/white
    } else {
        reserved = [0, 0x76, 0x9e, 0xb8]; // blue/cyan/green
    }
    */

    let keepers = zeroes(256);
    for (let i of reserved) {
        keepers[i & 0xfe] = 1; // drop that 0 luminance bit!
    }

    // Median cut!
    // https://en.wikipedia.org/wiki/Median_cut
    //let buckets = [input.slice()];

    // preface the reserved bits
    let buckets = reserved.slice().map((c) => [atariRGB[c]]).concat([input.slice()]);
    if (input.length != 160) {
        throw new Error('xxx bad input size');
    }

    /*
    let buckets = [input.slice()];
    if (reserved.length > 0) {
        let pxPerReserved = input.length;
        for (let c of reserved) {
            for (let i = 0; i < pxPerReserved; i++) {
                buckets[0].unshift(atariRGB[c]);
            }
        }
        console.log(buckets[0].length, 'xxx');
    }
    */

    let magicSort = (picker) => (a, b) => {
        let bychannel = picker(b) - picker(a);
        if (bychannel) return bychannel;

        let byluma = b.luma() - a.luma();
        return byluma;
    };
    let medianCut = (bucket, range) => {
        if (bucket.length < 2) {
            throw new Error('short bucket');
        }
        //console.log('medianCut', bucket, range);
        // Sort by the channel with the greatest range,
        // then cut the bucket in two at the median.
        if (range.g >= range.r && range.g >= range.b) {
            //bucket.sort((a, b) => b.g - a.g);
            bucket.sort(magicSort((rgb) => rgb.g));
        } else if (range.r >= range.g && range.r >= range.b) {
            //bucket.sort((a, b) => b.r - a.r);
            bucket.sort(magicSort((rgb) => rgb.r));
        } else if (range.b >= range.g && range.b >= range.r) {
            //bucket.sort((a, b) => b.b - a.b);
            bucket.sort(magicSort((rgb) => rgb.b));
        }
        let half = bucket.length >> 1;
        //console.log('cutting', half, bucket.length);
        let [bottom, top] = [bucket.slice(0, half), bucket.slice(half)];
        //console.log({bottom, top});
        return [bottom, top];
        //return [bucket.slice(0, half), bucket.slice(half)];
    };
    while (buckets.length < n) {
        // Find the bucket with the greatest range in any channel
        let ranges = buckets.map((bucket) => {
            if (bucket.length == 0) {
                throw new Error('xxx empty bucket');
            }
            let red   = bucket.map((rgb) => rgb.r);
            let green = bucket.map((rgb) => rgb.g);
            let blue  = bucket.map((rgb) => rgb.b);
            return new RGB(
                Math.max(...red)   - Math.min(...red),
                Math.max(...green) - Math.min(...green),
                Math.max(...blue)  - Math.min(...blue)
            );
        });
        let topRanges = ranges.map((rgb) => Math.max(rgb.r, rgb.g, rgb.b));
        //let greatest = Math.max(...topRanges);
        //let index = topRanges.indexOf(greatest);
        let greatest = 0;
        let index = -1;
        for (let i = 0; i < topRanges.length; i++) {
            //if (topRanges[i] >= greatest) {
            if (topRanges[i] > greatest) {
                greatest = topRanges[i];
                index = i;
            }
        }
        if (index == -1) {
            // We just ran out of colors! Pad the buckets.
            //while (buckets.length < n) {
            //    buckets.push([new RGB(0, 0, 0)]);
            //}
            break;
        }
        let [lo, hi] = medianCut(buckets[index], ranges[index]);
        buckets.splice(index, 1, lo, hi);
    }

    if (buckets.length > n) {
        throw new Error('xxx too many colors assigned');
    }
    decimated = buckets.map((bucket) => {
        // Average the RGB colors in this chunk
        let rgb = bucket
            .reduce((acc, rgb) => acc.inc(rgb), new RGB(0, 0, 0))
            .divide(bucket.length);

        // Scale the average to the brightest
        let avg_luma = rgb.luma();
        let lumas = bucket.map((rgb) => rgb.luma());
        let brightest = Math.max(...lumas);
        if (avg_luma > 0) {
            rgb = rgb.multiply(brightest / avg_luma).clamp();
        }

        // this also works pretty ok
        // but i think keeping luma is better
        //
        /*
        // 1) take the brightest luma
        // 2) take the most saturated chroma
        // 3) profit!
        let lumas = bucket.map((rgb) => rgb.luma());
        let brightest = Math.max(...lumas);
        let saturations = bucket.map((rgb) => Math.max(rgb.r, rgb.g, rgb.b) - Math.min(rgb.r, rgb.g, rgb.b));
        let saturation = Math.max(...saturations);
        let saturatedIndex = saturations.indexOf(saturation);
        let rgb = bucket[saturatedIndex];
        let luma = rgb.luma();
        if (luma > 0) {
            rgb = rgb.multiply(brightest / luma).clamp();
        }
        */
    
        // pick the luma-brightest color in the bucket
        // kinda nice but really aggressive with the colors
        /*
        let lumas = bucket.map((rgb) => rgb.luma());
        let luma = Math.max(...lumas);
        let rgb = bucket[lumas.indexOf(luma)];
        */

        // Take the channel-brightest color in the bucket
        // bad
        //let rgb = bucket[bucket.length - 1];

        // Take the luma-brightest color in the bucket
        // wrong? bad
        //let rgb = bucket.slice().sort((a, b) => b.luma() - a.luma())[bucket.length - 1];

        // Take the median color in the bucket
        // bad
        //let rgb = bucket[bucket.length >> 1];

        // Combine the brightest of each channel
        // this is kinda good
        /*
        let rgb = new RGB(
            Math.max(...bucket.map((rgb) => rgb.r)),
            Math.max(...bucket.map((rgb) => rgb.g)),
            Math.max(...bucket.map((rgb) => rgb.b))
        );
        */

        // combine the median of each channel
        // sux
        /*
        let rgb = new RGB(
            bucket.map((rgb) => rgb.r).sort((a, b) => b - a)[bucket.length >> 1],
            bucket.map((rgb) => rgb.g).sort((a, b) => b - a)[bucket.length >> 1],
            bucket.map((rgb) => rgb.b).sort((a, b) => b - a)[bucket.length >> 1]
        );
        */

        // Take the luma-median color in the bucket
        //let rgb = bucket.slice().sort((a, b) => b.luma() - a.luma())[bucket.length >> 1];

        // Take the brightest-channel median
        //let rgb = bucket.slice()
        //    .sort((a, b) => Math.max(b.r, b.g, b.b) - Math.max(a.r, b.g, b.b))[bucket.length >> 1];

        // And map into the Atari palette
        let dists = palette.map((i) => rgb.difference(atariRGB[i]).magnitude());
        let closest = Math.min(...dists);
        let index = dists.indexOf(closest);
        return palette[index];
    });
    decimated.sort((a, b) => a - b);

    // Palette fits
    return dither(decimated);
}

/**
 * Read an image file into a buffer
 * @param {string} src 
 * @returns {{width: number, height: number, rgba: Uint8Array}}
 */
async function loadImage(src) {
    let image = await Jimp.read(src);

    let width = image.bitmap.width;
    let height = image.bitmap.height;

    let aspect = width / height;
    let dar = 2 / 1.2;
    if (aspect > ((320 / 1.2) / 192)) {
        // wide
        width = 160;
        height = Math.round((width * image.bitmap.height / image.bitmap.width) * dar);
        if (height & 1) {
            height++;
        }
    } else {
        // tall
        height = 192;
        width = Math.round((height * image.bitmap.width / image.bitmap.height) / dar);
        if (width & 1) {
            width++;
        }
    }
    image = image.resize(width, height);

    let rgba = image.bitmap.data.slice();
    return {
        width,
        height,
        rgba,
    };
}

function imageToLinearRGB(rgba) {
    let input = [];
    for (let i = 0; i < rgba.length; i += 4) {
        input.push(new RGB(
            rgba[i + 0],
            rgba[i + 1],
            rgba[i + 2]
        ).fromSRGB());
    }
    return input;
}

/**
 * Read an image file, squish to 160px if necessary,
 * and dither to 4 colors per scan line.
 *
 * @param {string} source path to source image file
 * @returns {{width: number, height: number, lines: {palette: Array, output: Uint8Array}[]}}
 */
async function convert(source) {

    let {
        width,
        height,
        rgba
    } = await loadImage(source);

    if (width > 160) {
        throw new Error(`expected <160px width, got ${width} pixels`);
    }

    if (height > 192) {
        throw new Error(`expected <192px height, got ${height} pixels`);
    }

    if (rgba.length != width * 4 * height) {
        console.log(`
        width: ${width}
        height: ${height}
        rgba.length: ${rgba.length}`)
        throw new Error('inconsistent data size');
    }

    let input = imageToLinearRGB(rgba);

    if (input.length != width * height) {
        console.log(`
        width: ${width}
        height: ${height}
        rgba.length: ${input.length}`)
        throw new Error('inconsistent data size on input');
    }

    // Start with all colors usable with regular CTIA modes
    // (not the 16-luminance special mode on GTIA)
    let allColors = [];
    for (let i = 0; i < 256; i += 2) {
        allColors.push(i);
    }

    let left = [], right = [];
    let padding = 0;
    if (width < 160) {
        padding = 160 - width;

        let black = new RGB(0, 0, 0);
        left = repeat(black, padding >> 1);
        right = repeat(black, padding + 1 >> 1);
    }

    let lines = [];
    for (let y = 0; y < height; y++) {
        let inputLine = input
            .slice(y * width, (y + 1) * width);

        if (padding) {
            inputLine = left.concat(inputLine, right);
        }
        if (y > 0) {
            let error = lines[y - 1].error;
            inputLine = inputLine.map((rgb, x) => rgb.add(error[x]).clamp());
        }
        let line = decimate(inputLine, allColors, 4, y);
        lines.push(line);
    }
    return {
        width: width + padding,
        height,
        lines
    };
}


function indexedToBitmap(width, nbits, src, dest) {
    let nbytes = width * nbits / 8;
    let x = 0;
    for (let i = 0; i < nbytes; i++) {
        let a = 0;
        for (let b = 0; b < 8; b += nbits) {
            a <<= nbits;
            a |= src[x++];
        }
        dest[i] = a;
    }
}

function byte2byte(arr) {
    let lines = [];
    for (let i=0; i < arr.length; i++) {
        lines.push(`.byte ${arr[i]}`);
    }
    return lines.join('\n');
}

//let [even, odd] = [0, 1].map((bit) => (arr) => arr.filter((_item, index) => (index & 1) === bit));
function even(arr) {
    return arr.filter((_item, index) => !(index & 1));
}
function odd(arr) {
    return arr.filter((_item, index) => (index & 1));
}

function genAssembly(width, height, nbits, lines) {
    let stride = width * nbits / 8;
    let half = stride * height / 2;
    let frame = {
        palette1: new Uint8Array(height),
        palette2: new Uint8Array(height),
        palette3: new Uint8Array(height),
        bitmap: new Uint8Array(stride * height),
    };
    for (let y = 0; y < height; y++) {
        let base = 0;
        frame.palette1[y] = lines[y + base].palette[1];
        frame.palette2[y] = lines[y + base].palette[2];
        frame.palette3[y] = lines[y + base].palette[3];
        indexedToBitmap(
            width,
            nbits,
            lines[y + base].output,
            frame.bitmap.subarray(y * stride, (y + 1) * stride)
        );
    }

    return `.data
.export frame1_top
.export frame1_bottom

.export frame1_palette1_even
.export frame1_palette1_odd
.export frame1_palette2_even
.export frame1_palette2_odd
.export frame1_palette3_even
.export frame1_palette3_odd

.export displaylist

.segment "BUFFERS"

.align 4096
frame1_top:
${byte2byte(frame.bitmap.slice(0, half))}

.align 4096
frame1_bottom:
${byte2byte(frame.bitmap.slice(half))}

.align 128
frame1_palette1_even:
${byte2byte(even(frame.palette1))}

.align 128
frame1_palette1_odd:
${byte2byte(odd(frame.palette1))}

.align 128
frame1_palette2_even:
${byte2byte(even(frame.palette2))}

.align 128
frame1_palette2_odd:
${byte2byte(odd(frame.palette2))}

.align 128
frame1_palette3_even:
${byte2byte(even(frame.palette3))}

.align 128
frame1_palette3_odd:
${byte2byte(odd(frame.palette3))}




.align 1024
displaylist:
    ; 24 lines overscan
    .repeat 2
        .byte $70 ; 8 blank lines
    .endrep
    ; include a DLI to mark us as frame 0
    .byte $f0 ; 8 blank lines

    ; ${height} lines graphics
    ; ANTIC mode e (160px 2bpp, 1 scan line per line)
    .byte $4e
    .addr frame1_top
    .repeat ${height / 2 - 1}
        .byte $0e
    .endrep
    .byte $4e
    .addr frame1_bottom
    .repeat ${height / 2 - 1}
        .byte $0e
    .endrep

    .byte $41 ; jump and blank
    .addr displaylist
`;
}

/**
 * Double width and save as an image file
 * @param {number} width 
 * @param {number} height 
 * @param {{output: number[], palette: number[]}} lines 
 * @param {string} dest 
 */
async function saveImage(width, height, lines, dest) {
    let width2 = width * 2;
    let stride = width2 * 4;
    let rgba = new Uint8Array(stride * height);

    for (let y = 0; y < height; y++) {
        let {output, palette} = lines[y];
        for (let x = 0; x < width2; x++) {
            let i = x >> 1;
            if (i >= width) {
                throw new Error('i >= width');
            }
            //let rgb = atariRGB[palette[output[i]]].fromLinear();
            let rgb = atariRGB[palette[output[i]]].toSRGB();

            rgba[y * stride + x * 4 + 0] = rgb.r;
            rgba[y * stride + x * 4 + 1] = rgb.g;
            rgba[y * stride + x * 4 + 2] = rgb.b;
            rgba[y * stride + x * 4 + 3] = 255;
        }
    }

    let image = await new Promise((resolve, reject) => {
        new Jimp({
            data: rgba,
            width: width2,
            height,
        }, (err, image) => {
            if (err) reject(err);
            resolve(image);
        });
    });
    await image.resize(Math.round(width2 * 2 / 1.2), height * 2);
    await image.writeAsync(dest);
}

async function main() {
    if (process.argv.length < 3) {
        console.error("Usage: node dither-image.js source-image.jpg dest-asm.s");
        process.exit(1);
    }

    let nbits = 2;

    let {width, height, lines} = await convert(process.argv[2], nbits);

    let asm = genAssembly(width, height, nbits, lines);
    writeFileSync(process.argv[3], asm, "utf-8");

    await saveImage(width, height, lines, `${process.argv[3]}.png`);

    process.exit(0);
}

main();