init

core/decoders/copyrect.js

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+/*
+ * noVNC: HTML5 VNC client
+ * Copyright (C) 2019 The noVNC Authors
+ * Licensed under MPL 2.0 (see LICENSE.txt)
+ *
+ * See README.md for usage and integration instructions.
+ *
+ */
+
+export default class CopyRectDecoder {
+    decodeRect(x, y, width, height, sock, display, depth) {
+        if (sock.rQwait("COPYRECT", 4)) {
+            return false;
+        }
+
+        let deltaX = sock.rQshift16();
+        let deltaY = sock.rQshift16();
+
+        if ((width === 0) || (height === 0)) {
+            return true;
+        }
+
+        display.copyImage(deltaX, deltaY, x, y, width, height);
+
+        return true;
+    }
+}

core/decoders/hextile.js

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+/*
+ * noVNC: HTML5 VNC client
+ * Copyright (C) 2019 The noVNC Authors
+ * Licensed under MPL 2.0 (see LICENSE.txt)
+ *
+ * See README.md for usage and integration instructions.
+ *
+ */
+
+import * as Log from '../util/logging.js';
+
+export default class HextileDecoder {
+    constructor() {
+        this._tiles = 0;
+        this._lastsubencoding = 0;
+        this._tileBuffer = new Uint8Array(16 * 16 * 4);
+    }
+
+    decodeRect(x, y, width, height, sock, display, depth) {
+        if (this._tiles === 0) {
+            this._tilesX = Math.ceil(width / 16);
+            this._tilesY = Math.ceil(height / 16);
+            this._totalTiles = this._tilesX * this._tilesY;
+            this._tiles = this._totalTiles;
+        }
+
+        while (this._tiles > 0) {
+            let bytes = 1;
+
+            if (sock.rQwait("HEXTILE", bytes)) {
+                return false;
+            }
+
+            let subencoding = sock.rQpeek8();
+            if (subencoding > 30) {  // Raw
+                throw new Error("Illegal hextile subencoding (subencoding: " +
+                            subencoding + ")");
+            }
+
+            const currTile = this._totalTiles - this._tiles;
+            const tileX = currTile % this._tilesX;
+            const tileY = Math.floor(currTile / this._tilesX);
+            const tx = x + tileX * 16;
+            const ty = y + tileY * 16;
+            const tw = Math.min(16, (x + width) - tx);
+            const th = Math.min(16, (y + height) - ty);
+
+            // Figure out how much we are expecting
+            if (subencoding & 0x01) {  // Raw
+                bytes += tw * th * 4;
+            } else {
+                if (subencoding & 0x02) {  // Background
+                    bytes += 4;
+                }
+                if (subencoding & 0x04) {  // Foreground
+                    bytes += 4;
+                }
+                if (subencoding & 0x08) {  // AnySubrects
+                    bytes++;  // Since we aren't shifting it off
+
+                    if (sock.rQwait("HEXTILE", bytes)) {
+                        return false;
+                    }
+
+                    let subrects = sock.rQpeekBytes(bytes).at(-1);
+                    if (subencoding & 0x10) {  // SubrectsColoured
+                        bytes += subrects * (4 + 2);
+                    } else {
+                        bytes += subrects * 2;
+                    }
+                }
+            }
+
+            if (sock.rQwait("HEXTILE", bytes)) {
+                return false;
+            }
+
+            // We know the encoding and have a whole tile
+            sock.rQshift8();
+            if (subencoding === 0) {
+                if (this._lastsubencoding & 0x01) {
+                    // Weird: ignore blanks are RAW
+                    Log.Debug("     Ignoring blank after RAW");
+                } else {
+                    display.fillRect(tx, ty, tw, th, this._background);
+                }
+            } else if (subencoding & 0x01) {  // Raw
+                let pixels = tw * th;
+                let data = sock.rQshiftBytes(pixels * 4, false);
+                // Max sure the image is fully opaque
+                for (let i = 0;i <  pixels;i++) {
+                    data[i * 4 + 3] = 255;
+                }
+                display.blitImage(tx, ty, tw, th, data, 0);
+            } else {
+                if (subencoding & 0x02) {  // Background
+                    this._background = new Uint8Array(sock.rQshiftBytes(4));
+                }
+                if (subencoding & 0x04) {  // Foreground
+                    this._foreground = new Uint8Array(sock.rQshiftBytes(4));
+                }
+
+                this._startTile(tx, ty, tw, th, this._background);
+                if (subencoding & 0x08) {  // AnySubrects
+                    let subrects = sock.rQshift8();
+
+                    for (let s = 0; s < subrects; s++) {
+                        let color;
+                        if (subencoding & 0x10) {  // SubrectsColoured
+                            color = sock.rQshiftBytes(4);
+                        } else {
+                            color = this._foreground;
+                        }
+                        const xy = sock.rQshift8();
+                        const sx = (xy >> 4);
+                        const sy = (xy & 0x0f);
+
+                        const wh = sock.rQshift8();
+                        const sw = (wh >> 4) + 1;
+                        const sh = (wh & 0x0f) + 1;
+
+                        this._subTile(sx, sy, sw, sh, color);
+                    }
+                }
+                this._finishTile(display);
+            }
+            this._lastsubencoding = subencoding;
+            this._tiles--;
+        }
+
+        return true;
+    }
+
+    // start updating a tile
+    _startTile(x, y, width, height, color) {
+        this._tileX = x;
+        this._tileY = y;
+        this._tileW = width;
+        this._tileH = height;
+
+        const red = color[0];
+        const green = color[1];
+        const blue = color[2];
+
+        const data = this._tileBuffer;
+        for (let i = 0; i < width * height * 4; i += 4) {
+            data[i]     = red;
+            data[i + 1] = green;
+            data[i + 2] = blue;
+            data[i + 3] = 255;
+        }
+    }
+
+    // update sub-rectangle of the current tile
+    _subTile(x, y, w, h, color) {
+        const red = color[0];
+        const green = color[1];
+        const blue = color[2];
+        const xend = x + w;
+        const yend = y + h;
+
+        const data = this._tileBuffer;
+        const width = this._tileW;
+        for (let j = y; j < yend; j++) {
+            for (let i = x; i < xend; i++) {
+                const p = (i + (j * width)) * 4;
+                data[p]     = red;
+                data[p + 1] = green;
+                data[p + 2] = blue;
+                data[p + 3] = 255;
+            }
+        }
+    }
+
+    // draw the current tile to the screen
+    _finishTile(display) {
+        display.blitImage(this._tileX, this._tileY,
+                          this._tileW, this._tileH,
+                          this._tileBuffer, 0);
+    }
+}

core/decoders/jpeg.js

@@ -0,0 +1,146 @@
+/*
+ * noVNC: HTML5 VNC client
+ * Copyright (C) 2019 The noVNC Authors
+ * Licensed under MPL 2.0 (see LICENSE.txt)
+ *
+ * See README.md for usage and integration instructions.
+ *
+ */
+
+export default class JPEGDecoder {
+    constructor() {
+        // RealVNC will reuse the quantization tables
+        // and Huffman tables, so we need to cache them.
+        this._cachedQuantTables = [];
+        this._cachedHuffmanTables = [];
+
+        this._segments = [];
+    }
+
+    decodeRect(x, y, width, height, sock, display, depth) {
+        // A rect of JPEG encodings is simply a JPEG file
+        while (true) {
+            let segment = this._readSegment(sock);
+            if (segment === null) {
+                return false;
+            }
+            this._segments.push(segment);
+            // End of image?
+            if (segment[1] === 0xD9) {
+                break;
+            }
+        }
+
+        let huffmanTables = [];
+        let quantTables = [];
+        for (let segment of this._segments) {
+            let type = segment[1];
+            if (type === 0xC4) {
+                // Huffman tables
+                huffmanTables.push(segment);
+            } else if (type === 0xDB) {
+                // Quantization tables
+                quantTables.push(segment);
+            }
+        }
+
+        const sofIndex = this._segments.findIndex(
+            x => x[1] == 0xC0 || x[1] == 0xC2
+        );
+        if (sofIndex == -1) {
+            throw new Error("Illegal JPEG image without SOF");
+        }
+
+        if (quantTables.length === 0) {
+            this._segments.splice(sofIndex+1, 0,
+                                  ...this._cachedQuantTables);
+        }
+        if (huffmanTables.length === 0) {
+            this._segments.splice(sofIndex+1, 0,
+                                  ...this._cachedHuffmanTables);
+        }
+
+        let length = 0;
+        for (let segment of this._segments) {
+            length += segment.length;
+        }
+
+        let data = new Uint8Array(length);
+        length = 0;
+        for (let segment of this._segments) {
+            data.set(segment, length);
+            length += segment.length;
+        }
+
+        display.imageRect(x, y, width, height, "image/jpeg", data);
+
+        if (huffmanTables.length !== 0) {
+            this._cachedHuffmanTables = huffmanTables;
+        }
+        if (quantTables.length !== 0) {
+            this._cachedQuantTables = quantTables;
+        }
+
+        this._segments = [];
+
+        return true;
+    }
+
+    _readSegment(sock) {
+        if (sock.rQwait("JPEG", 2)) {
+            return null;
+        }
+
+        let marker = sock.rQshift8();
+        if (marker != 0xFF) {
+            throw new Error("Illegal JPEG marker received (byte: " +
+                               marker + ")");
+        }
+        let type = sock.rQshift8();
+        if (type >= 0xD0 && type <= 0xD9 || type == 0x01) {
+            // No length after marker
+            return new Uint8Array([marker, type]);
+        }
+
+        if (sock.rQwait("JPEG", 2, 2)) {
+            return null;
+        }
+
+        let length = sock.rQshift16();
+        if (length < 2) {
+            throw new Error("Illegal JPEG length received (length: " +
+                               length + ")");
+        }
+
+        if (sock.rQwait("JPEG", length-2, 4)) {
+            return null;
+        }
+
+        let extra = 0;
+        if (type === 0xDA) {
+            // start of scan
+            extra += 2;
+            while (true) {
+                if (sock.rQwait("JPEG", length-2+extra, 4)) {
+                    return null;
+                }
+                let data = sock.rQpeekBytes(length-2+extra, false);
+                if (data.at(-2) === 0xFF && data.at(-1) !== 0x00 &&
+                    !(data.at(-1) >= 0xD0 && data.at(-1) <= 0xD7)) {
+                    extra -= 2;
+                    break;
+                }
+                extra++;
+            }
+        }
+
+        let segment = new Uint8Array(2 + length + extra);
+        segment[0] = marker;
+        segment[1] = type;
+        segment[2] = length >> 8;
+        segment[3] = length;
+        segment.set(sock.rQshiftBytes(length-2+extra, false), 4);
+
+        return segment;
+    }
+}

core/decoders/raw.js

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+/*
+ * noVNC: HTML5 VNC client
+ * Copyright (C) 2019 The noVNC Authors
+ * Licensed under MPL 2.0 (see LICENSE.txt)
+ *
+ * See README.md for usage and integration instructions.
+ *
+ */
+
+export default class RawDecoder {
+    constructor() {
+        this._lines = 0;
+    }
+
+    decodeRect(x, y, width, height, sock, display, depth) {
+        if ((width === 0) || (height === 0)) {
+            return true;
+        }
+
+        if (this._lines === 0) {
+            this._lines = height;
+        }
+
+        const pixelSize = depth == 8 ? 1 : 4;
+        const bytesPerLine = width * pixelSize;
+
+        while (this._lines > 0) {
+            if (sock.rQwait("RAW", bytesPerLine)) {
+                return false;
+            }
+
+            const curY = y + (height - this._lines);
+
+            let data = sock.rQshiftBytes(bytesPerLine, false);
+
+            // Convert data if needed
+            if (depth == 8) {
+                const newdata = new Uint8Array(width * 4);
+                for (let i = 0; i < width; i++) {
+                    newdata[i * 4 + 0] = ((data[i] >> 0) & 0x3) * 255 / 3;
+                    newdata[i * 4 + 1] = ((data[i] >> 2) & 0x3) * 255 / 3;
+                    newdata[i * 4 + 2] = ((data[i] >> 4) & 0x3) * 255 / 3;
+                    newdata[i * 4 + 3] = 255;
+                }
+                data = newdata;
+            }
+
+            // Max sure the image is fully opaque
+            for (let i = 0; i < width; i++) {
+                data[i * 4 + 3] = 255;
+            }
+
+            display.blitImage(x, curY, width, 1, data, 0);
+            this._lines--;
+        }
+
+        return true;
+    }
+}

core/decoders/rre.js

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+/*
+ * noVNC: HTML5 VNC client
+ * Copyright (C) 2019 The noVNC Authors
+ * Licensed under MPL 2.0 (see LICENSE.txt)
+ *
+ * See README.md for usage and integration instructions.
+ *
+ */
+
+export default class RREDecoder {
+    constructor() {
+        this._subrects = 0;
+    }
+
+    decodeRect(x, y, width, height, sock, display, depth) {
+        if (this._subrects === 0) {
+            if (sock.rQwait("RRE", 4 + 4)) {
+                return false;
+            }
+
+            this._subrects = sock.rQshift32();
+
+            let color = sock.rQshiftBytes(4);  // Background
+            display.fillRect(x, y, width, height, color);
+        }
+
+        while (this._subrects > 0) {
+            if (sock.rQwait("RRE", 4 + 8)) {
+                return false;
+            }
+
+            let color = sock.rQshiftBytes(4);
+            let sx = sock.rQshift16();
+            let sy = sock.rQshift16();
+            let swidth = sock.rQshift16();
+            let sheight = sock.rQshift16();
+            display.fillRect(x + sx, y + sy, swidth, sheight, color);
+
+            this._subrects--;
+        }
+
+        return true;
+    }
+}

core/decoders/tight.js

@@ -0,0 +1,393 @@
+/*
+ * noVNC: HTML5 VNC client
+ * Copyright (C) 2019 The noVNC Authors
+ * (c) 2012 Michael Tinglof, Joe Balaz, Les Piech (Mercuri.ca)
+ * Licensed under MPL 2.0 (see LICENSE.txt)
+ *
+ * See README.md for usage and integration instructions.
+ *
+ */
+
+import * as Log from '../util/logging.js';
+import Inflator from "../inflator.js";
+
+export default class TightDecoder {
+    constructor() {
+        this._ctl = null;
+        this._filter = null;
+        this._numColors = 0;
+        this._palette = new Uint8Array(1024);  // 256 * 4 (max palette size * max bytes-per-pixel)
+        this._len = 0;
+
+        this._zlibs = [];
+        for (let i = 0; i < 4; i++) {
+            this._zlibs[i] = new Inflator();
+        }
+    }
+
+    decodeRect(x, y, width, height, sock, display, depth) {
+        if (this._ctl === null) {
+            if (sock.rQwait("TIGHT compression-control", 1)) {
+                return false;
+            }
+
+            this._ctl = sock.rQshift8();
+
+            // Reset streams if the server requests it
+            for (let i = 0; i < 4; i++) {
+                if ((this._ctl >> i) & 1) {
+                    this._zlibs[i].reset();
+                    Log.Info("Reset zlib stream " + i);
+                }
+            }
+
+            // Figure out filter
+            this._ctl = this._ctl >> 4;
+        }
+
+        let ret;
+
+        if (this._ctl === 0x08) {
+            ret = this._fillRect(x, y, width, height,
+                                 sock, display, depth);
+        } else if (this._ctl === 0x09) {
+            ret = this._jpegRect(x, y, width, height,
+                                 sock, display, depth);
+        } else if (this._ctl === 0x0A) {
+            ret = this._pngRect(x, y, width, height,
+                                sock, display, depth);
+        } else if ((this._ctl & 0x08) == 0) {
+            ret = this._basicRect(this._ctl, x, y, width, height,
+                                  sock, display, depth);
+        } else {
+            throw new Error("Illegal tight compression received (ctl: " +
+                                   this._ctl + ")");
+        }
+
+        if (ret) {
+            this._ctl = null;
+        }
+
+        return ret;
+    }
+
+    _fillRect(x, y, width, height, sock, display, depth) {
+        if (sock.rQwait("TIGHT", 3)) {
+            return false;
+        }
+
+        let pixel = sock.rQshiftBytes(3);
+        display.fillRect(x, y, width, height, pixel, false);
+
+        return true;
+    }
+
+    _jpegRect(x, y, width, height, sock, display, depth) {
+        let data = this._readData(sock);
+        if (data === null) {
+            return false;
+        }
+
+        display.imageRect(x, y, width, height, "image/jpeg", data);
+
+        return true;
+    }
+
+    _pngRect(x, y, width, height, sock, display, depth) {
+        throw new Error("PNG received in standard Tight rect");
+    }
+
+    _basicRect(ctl, x, y, width, height, sock, display, depth) {
+        if (this._filter === null) {
+            if (ctl & 0x4) {
+                if (sock.rQwait("TIGHT", 1)) {
+                    return false;
+                }
+
+                this._filter = sock.rQshift8();
+            } else {
+                // Implicit CopyFilter
+                this._filter = 0;
+            }
+        }
+
+        let streamId = ctl & 0x3;
+
+        let ret;
+
+        switch (this._filter) {
+            case 0: // CopyFilter
+                ret = this._copyFilter(streamId, x, y, width, height,
+                                       sock, display, depth);
+                break;
+            case 1: // PaletteFilter
+                ret = this._paletteFilter(streamId, x, y, width, height,
+                                          sock, display, depth);
+                break;
+            case 2: // GradientFilter
+                ret = this._gradientFilter(streamId, x, y, width, height,
+                                           sock, display, depth);
+                break;
+            default:
+                throw new Error("Illegal tight filter received (ctl: " +
+                                       this._filter + ")");
+        }
+
+        if (ret) {
+            this._filter = null;
+        }
+
+        return ret;
+    }
+
+    _copyFilter(streamId, x, y, width, height, sock, display, depth) {
+        const uncompressedSize = width * height * 3;
+        let data;
+
+        if (uncompressedSize === 0) {
+            return true;
+        }
+
+        if (uncompressedSize < 12) {
+            if (sock.rQwait("TIGHT", uncompressedSize)) {
+                return false;
+            }
+
+            data = sock.rQshiftBytes(uncompressedSize);
+        } else {
+            data = this._readData(sock);
+            if (data === null) {
+                return false;
+            }
+
+            this._zlibs[streamId].setInput(data);
+            data = this._zlibs[streamId].inflate(uncompressedSize);
+            this._zlibs[streamId].setInput(null);
+        }
+
+        let rgbx = new Uint8Array(width * height * 4);
+        for (let i = 0, j = 0; i < width * height * 4; i += 4, j += 3) {
+            rgbx[i]     = data[j];
+            rgbx[i + 1] = data[j + 1];
+            rgbx[i + 2] = data[j + 2];
+            rgbx[i + 3] = 255;  // Alpha
+        }
+
+        display.blitImage(x, y, width, height, rgbx, 0, false);
+
+        return true;
+    }
+
+    _paletteFilter(streamId, x, y, width, height, sock, display, depth) {
+        if (this._numColors === 0) {
+            if (sock.rQwait("TIGHT palette", 1)) {
+                return false;
+            }
+
+            const numColors = sock.rQpeek8() + 1;
+            const paletteSize = numColors * 3;
+
+            if (sock.rQwait("TIGHT palette", 1 + paletteSize)) {
+                return false;
+            }
+
+            this._numColors = numColors;
+            sock.rQskipBytes(1);
+
+            sock.rQshiftTo(this._palette, paletteSize);
+        }
+
+        const bpp = (this._numColors <= 2) ? 1 : 8;
+        const rowSize = Math.floor((width * bpp + 7) / 8);
+        const uncompressedSize = rowSize * height;
+
+        let data;
+
+        if (uncompressedSize === 0) {
+            return true;
+        }
+
+        if (uncompressedSize < 12) {
+            if (sock.rQwait("TIGHT", uncompressedSize)) {
+                return false;
+            }
+
+            data = sock.rQshiftBytes(uncompressedSize);
+        } else {
+            data = this._readData(sock);
+            if (data === null) {
+                return false;
+            }
+
+            this._zlibs[streamId].setInput(data);
+            data = this._zlibs[streamId].inflate(uncompressedSize);
+            this._zlibs[streamId].setInput(null);
+        }
+
+        // Convert indexed (palette based) image data to RGB
+        if (this._numColors == 2) {
+            this._monoRect(x, y, width, height, data, this._palette, display);
+        } else {
+            this._paletteRect(x, y, width, height, data, this._palette, display);
+        }
+
+        this._numColors = 0;
+
+        return true;
+    }
+
+    _monoRect(x, y, width, height, data, palette, display) {
+        // Convert indexed (palette based) image data to RGB
+        // TODO: reduce number of calculations inside loop
+        const dest = this._getScratchBuffer(width * height * 4);
+        const w = Math.floor((width + 7) / 8);
+        const w1 = Math.floor(width / 8);
+
+        for (let y = 0; y < height; y++) {
+            let dp, sp, x;
+            for (x = 0; x < w1; x++) {
+                for (let b = 7; b >= 0; b--) {
+                    dp = (y * width + x * 8 + 7 - b) * 4;
+                    sp = (data[y * w + x] >> b & 1) * 3;
+                    dest[dp]     = palette[sp];
+                    dest[dp + 1] = palette[sp + 1];
+                    dest[dp + 2] = palette[sp + 2];
+                    dest[dp + 3] = 255;
+                }
+            }
+
+            for (let b = 7; b >= 8 - width % 8; b--) {
+                dp = (y * width + x * 8 + 7 - b) * 4;
+                sp = (data[y * w + x] >> b & 1) * 3;
+                dest[dp]     = palette[sp];
+                dest[dp + 1] = palette[sp + 1];
+                dest[dp + 2] = palette[sp + 2];
+                dest[dp + 3] = 255;
+            }
+        }
+
+        display.blitImage(x, y, width, height, dest, 0, false);
+    }
+
+    _paletteRect(x, y, width, height, data, palette, display) {
+        // Convert indexed (palette based) image data to RGB
+        const dest = this._getScratchBuffer(width * height * 4);
+        const total = width * height * 4;
+        for (let i = 0, j = 0; i < total; i += 4, j++) {
+            const sp = data[j] * 3;
+            dest[i]     = palette[sp];
+            dest[i + 1] = palette[sp + 1];
+            dest[i + 2] = palette[sp + 2];
+            dest[i + 3] = 255;
+        }
+
+        display.blitImage(x, y, width, height, dest, 0, false);
+    }
+
+    _gradientFilter(streamId, x, y, width, height, sock, display, depth) {
+        // assume the TPIXEL is 3 bytes long
+        const uncompressedSize = width * height * 3;
+        let data;
+
+        if (uncompressedSize === 0) {
+            return true;
+        }
+
+        if (uncompressedSize < 12) {
+            if (sock.rQwait("TIGHT", uncompressedSize)) {
+                return false;
+            }
+
+            data = sock.rQshiftBytes(uncompressedSize);
+        } else {
+            data = this._readData(sock);
+            if (data === null) {
+                return false;
+            }
+
+            this._zlibs[streamId].setInput(data);
+            data = this._zlibs[streamId].inflate(uncompressedSize);
+            this._zlibs[streamId].setInput(null);
+        }
+
+        let rgbx = new Uint8Array(4 * width * height);
+
+        let rgbxIndex = 0, dataIndex = 0;
+        let left = new Uint8Array(3);
+        for (let x = 0; x < width; x++) {
+            for (let c = 0; c < 3; c++) {
+                const prediction = left[c];
+                const value = data[dataIndex++] + prediction;
+                rgbx[rgbxIndex++] = value;
+                left[c] = value;
+            }
+            rgbx[rgbxIndex++] = 255;
+        }
+
+        let upperIndex = 0;
+        let upper = new Uint8Array(3),
+            upperleft = new Uint8Array(3);
+        for (let y = 1; y < height; y++) {
+            left.fill(0);
+            upperleft.fill(0);
+            for (let x = 0; x < width; x++) {
+                for (let c = 0; c < 3; c++) {
+                    upper[c] = rgbx[upperIndex++];
+                    let prediction = left[c] + upper[c] - upperleft[c];
+                    if (prediction < 0) {
+                        prediction = 0;
+                    } else if (prediction > 255) {
+                        prediction = 255;
+                    }
+                    const value = data[dataIndex++] + prediction;
+                    rgbx[rgbxIndex++] = value;
+                    upperleft[c] = upper[c];
+                    left[c] = value;
+                }
+                rgbx[rgbxIndex++] = 255;
+                upperIndex++;
+            }
+        }
+
+        display.blitImage(x, y, width, height, rgbx, 0, false);
+
+        return true;
+    }
+
+    _readData(sock) {
+        if (this._len === 0) {
+            if (sock.rQwait("TIGHT", 3)) {
+                return null;
+            }
+
+            let byte;
+
+            byte = sock.rQshift8();
+            this._len = byte & 0x7f;
+            if (byte & 0x80) {
+                byte = sock.rQshift8();
+                this._len |= (byte & 0x7f) << 7;
+                if (byte & 0x80) {
+                    byte = sock.rQshift8();
+                    this._len |= byte << 14;
+                }
+            }
+        }
+
+        if (sock.rQwait("TIGHT", this._len)) {
+            return null;
+        }
+
+        let data = sock.rQshiftBytes(this._len, false);
+        this._len = 0;
+
+        return data;
+    }
+
+    _getScratchBuffer(size) {
+        if (!this._scratchBuffer || (this._scratchBuffer.length < size)) {
+            this._scratchBuffer = new Uint8Array(size);
+        }
+        return this._scratchBuffer;
+    }
+}

core/decoders/tightpng.js

@@ -0,0 +1,27 @@
+/*
+ * noVNC: HTML5 VNC client
+ * Copyright (C) 2019 The noVNC Authors
+ * Licensed under MPL 2.0 (see LICENSE.txt)
+ *
+ * See README.md for usage and integration instructions.
+ *
+ */
+
+import TightDecoder from './tight.js';
+
+export default class TightPNGDecoder extends TightDecoder {
+    _pngRect(x, y, width, height, sock, display, depth) {
+        let data = this._readData(sock);
+        if (data === null) {
+            return false;
+        }
+
+        display.imageRect(x, y, width, height, "image/png", data);
+
+        return true;
+    }
+
+    _basicRect(ctl, x, y, width, height, sock, display, depth) {
+        throw new Error("BasicCompression received in TightPNG rect");
+    }
+}

core/decoders/zrle.js

@@ -0,0 +1,185 @@
+/*
+ * noVNC: HTML5 VNC client
+ * Copyright (C) 2021 The noVNC Authors
+ * Licensed under MPL 2.0 (see LICENSE.txt)
+ *
+ * See README.md for usage and integration instructions.
+ *
+ */
+
+import Inflate from "../inflator.js";
+
+const ZRLE_TILE_WIDTH = 64;
+const ZRLE_TILE_HEIGHT = 64;
+
+export default class ZRLEDecoder {
+    constructor() {
+        this._length = 0;
+        this._inflator = new Inflate();
+
+        this._pixelBuffer = new Uint8Array(ZRLE_TILE_WIDTH * ZRLE_TILE_HEIGHT * 4);
+        this._tileBuffer = new Uint8Array(ZRLE_TILE_WIDTH * ZRLE_TILE_HEIGHT * 4);
+    }
+
+    decodeRect(x, y, width, height, sock, display, depth) {
+        if (this._length === 0) {
+            if (sock.rQwait("ZLib data length", 4)) {
+                return false;
+            }
+            this._length = sock.rQshift32();
+        }
+        if (sock.rQwait("Zlib data", this._length)) {
+            return false;
+        }
+
+        const data = sock.rQshiftBytes(this._length, false);
+
+        this._inflator.setInput(data);
+
+        for (let ty = y; ty < y + height; ty += ZRLE_TILE_HEIGHT) {
+            let th = Math.min(ZRLE_TILE_HEIGHT, y + height - ty);
+
+            for (let tx = x; tx < x + width; tx += ZRLE_TILE_WIDTH) {
+                let tw = Math.min(ZRLE_TILE_WIDTH, x + width - tx);
+
+                const tileSize = tw * th;
+                const subencoding = this._inflator.inflate(1)[0];
+                if (subencoding === 0) {
+                    // raw data
+                    const data = this._readPixels(tileSize);
+                    display.blitImage(tx, ty, tw, th, data, 0, false);
+                } else if (subencoding === 1) {
+                    // solid
+                    const background = this._readPixels(1);
+                    display.fillRect(tx, ty, tw, th, [background[0], background[1], background[2]]);
+                } else if (subencoding >= 2 && subencoding <= 16) {
+                    const data = this._decodePaletteTile(subencoding, tileSize, tw, th);
+                    display.blitImage(tx, ty, tw, th, data, 0, false);
+                } else if (subencoding === 128) {
+                    const data = this._decodeRLETile(tileSize);
+                    display.blitImage(tx, ty, tw, th, data, 0, false);
+                } else if (subencoding >= 130 && subencoding <= 255) {
+                    const data = this._decodeRLEPaletteTile(subencoding - 128, tileSize);
+                    display.blitImage(tx, ty, tw, th, data, 0, false);
+                } else {
+                    throw new Error('Unknown subencoding: ' + subencoding);
+                }
+            }
+        }
+        this._length = 0;
+        return true;
+    }
+
+    _getBitsPerPixelInPalette(paletteSize) {
+        if (paletteSize <= 2) {
+            return 1;
+        } else if (paletteSize <= 4) {
+            return 2;
+        } else if (paletteSize <= 16) {
+            return 4;
+        }
+    }
+
+    _readPixels(pixels) {
+        let data = this._pixelBuffer;
+        const buffer = this._inflator.inflate(3*pixels);
+        for (let i = 0, j = 0; i < pixels*4; i += 4, j += 3) {
+            data[i]     = buffer[j];
+            data[i + 1] = buffer[j + 1];
+            data[i + 2] = buffer[j + 2];
+            data[i + 3] = 255;  // Add the Alpha
+        }
+        return data;
+    }
+
+    _decodePaletteTile(paletteSize, tileSize, tilew, tileh) {
+        const data = this._tileBuffer;
+        const palette = this._readPixels(paletteSize);
+        const bitsPerPixel = this._getBitsPerPixelInPalette(paletteSize);
+        const mask = (1 << bitsPerPixel) - 1;
+
+        let offset = 0;
+        let encoded = this._inflator.inflate(1)[0];
+
+        for (let y=0; y<tileh; y++) {
+            let shift = 8-bitsPerPixel;
+            for (let x=0; x<tilew; x++) {
+                if (shift<0) {
+                    shift=8-bitsPerPixel;
+                    encoded = this._inflator.inflate(1)[0];
+                }
+                let indexInPalette = (encoded>>shift) & mask;
+
+                data[offset] = palette[indexInPalette * 4];
+                data[offset + 1] = palette[indexInPalette * 4 + 1];
+                data[offset + 2] = palette[indexInPalette * 4 + 2];
+                data[offset + 3] = palette[indexInPalette * 4 + 3];
+                offset += 4;
+                shift-=bitsPerPixel;
+            }
+            if (shift<8-bitsPerPixel && y<tileh-1) {
+                encoded =  this._inflator.inflate(1)[0];
+            }
+        }
+        return data;
+    }
+
+    _decodeRLETile(tileSize) {
+        const data = this._tileBuffer;
+        let i = 0;
+        while (i < tileSize) {
+            const pixel = this._readPixels(1);
+            const length = this._readRLELength();
+            for (let j = 0; j < length; j++) {
+                data[i * 4] = pixel[0];
+                data[i * 4 + 1] = pixel[1];
+                data[i * 4 + 2] = pixel[2];
+                data[i * 4 + 3] = pixel[3];
+                i++;
+            }
+        }
+        return data;
+    }
+
+    _decodeRLEPaletteTile(paletteSize, tileSize) {
+        const data = this._tileBuffer;
+
+        // palette
+        const palette = this._readPixels(paletteSize);
+
+        let offset = 0;
+        while (offset < tileSize) {
+            let indexInPalette = this._inflator.inflate(1)[0];
+            let length = 1;
+            if (indexInPalette >= 128) {
+                indexInPalette -= 128;
+                length = this._readRLELength();
+            }
+            if (indexInPalette > paletteSize) {
+                throw new Error('Too big index in palette: ' + indexInPalette + ', palette size: ' + paletteSize);
+            }
+            if (offset + length > tileSize) {
+                throw new Error('Too big rle length in palette mode: ' + length + ', allowed length is: ' + (tileSize - offset));
+            }
+
+            for (let j = 0; j < length; j++) {
+                data[offset * 4] = palette[indexInPalette * 4];
+                data[offset * 4 + 1] = palette[indexInPalette * 4 + 1];
+                data[offset * 4 + 2] = palette[indexInPalette * 4 + 2];
+                data[offset * 4 + 3] = palette[indexInPalette * 4 + 3];
+                offset++;
+            }
+        }
+        return data;
+    }
+
+    _readRLELength() {
+        let length = 0;
+        let current = 0;
+        do {
+            current = this._inflator.inflate(1)[0];
+            length += current;
+        } while (current === 255);
+        return length + 1;
+    }
+}