private void decodeBitmapData(GifFrame frame) {
        if (frame != null) {
            // Jump to the frame start position.
            rawData.position(frame.bufferFrameStart);
        }

        int npix = (frame == null) ? header.width * header.height : frame.iw * frame.ih;
        int available, clear, codeMask, codeSize, endOfInformation, inCode, oldCode, bits, code, count, i, datum,
                dataSize, first, top, bi, pi;

        if (mainPixels == null || mainPixels.length < npix) {
            // Allocate new pixel array.
            mainPixels = new byte[npix];
        }
        if (prefix == null) {
            prefix = new short[MAX_STACK_SIZE];
        }
        if (suffix == null) {
            suffix = new byte[MAX_STACK_SIZE];
        }
        if (pixelStack == null) {
            pixelStack = new byte[MAX_STACK_SIZE + 1];
        }

        // Initialize GIF data stream decoder.
        dataSize = read();
        clear = 1 << dataSize;
        endOfInformation = clear + 1;
        available = clear + 2;
        oldCode = NULL_CODE;
        codeSize = dataSize + 1;
        codeMask = (1 << codeSize) - 1;
        for (code = 0; code < clear; code++) {
            // XXX ArrayIndexOutOfBoundsException.
            prefix[code] = 0;
            suffix[code] = (byte) code;
        }

        // Decode GIF pixel stream.
        datum = bits = count = first = top = pi = bi = 0;
        for (i = 0; i < npix; ) {
            // Load bytes until there are enough bits for a code.
            if (count == 0) {
                // Read a new data block.
                count = readBlock();
                if (count <= 0) {
                    status = STATUS_PARTIAL_DECODE;
                    break;
                }
                bi = 0;
            }

            datum += (((int) block[bi]) & 0xff) << bits;
            bits += 8;
            bi++;
            count--;

            while (bits >= codeSize) {
                // Get the next code.
                code = datum & codeMask;
                datum >>= codeSize;
                bits -= codeSize;

                // Interpret the code.
                if (code == clear) {
                    // Reset decoder.
                    codeSize = dataSize + 1;
                    codeMask = (1 << codeSize) - 1;
                    available = clear + 2;
                    oldCode = NULL_CODE;
                    continue;
                }

                if (code > available) {
                    status = STATUS_PARTIAL_DECODE;
                    break;
                }

                if (code == endOfInformation) {
                    break;
                }

                if (oldCode == NULL_CODE) {
                    pixelStack[top++] = suffix[code];
                    oldCode = code;
                    first = code;
                    continue;
                }
                inCode = code;
                if (code >= available) {
                    pixelStack[top++] = (byte) first;
                    code = oldCode;
                }
                while (code >= clear) {
                    pixelStack[top++] = suffix[code];
                    code = prefix[code];
                }
                first = ((int) suffix[code]) & 0xff;
                pixelStack[top++] = (byte) first;

                // Add a new string to the string table.
                if (available < MAX_STACK_SIZE) {
                    prefix[available] = (short) oldCode;
                    suffix[available] = (byte) first;
                    available++;
                    if (((available & codeMask) == 0) && (available < MAX_STACK_SIZE)) {
                        codeSize++;
                        codeMask += available;
                    }
                }
                oldCode = inCode;

                while (top > 0) {
                    // Pop a pixel off the pixel stack.
                    top--;
                    mainPixels[pi++] = pixelStack[top];
                    i++;
                }
            }
        }

        // Clear missing pixels.
        for (i = pi; i < npix; i++) {
            mainPixels[i] = 0;
        }
    }
Decodes LZW image data into pixel array. Adapted from John Cristy's BitmapMagick.
core/src/main/java/com/bumptech/glide/gifdecoder/GifDecoder.java