tight.c

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                pixHere[c] = (int)(pix >> shiftBits[c] & maxColor[c]);   \
                *prevRowPtr++ = pixHere[c];                              \
                                                                         \
                prediction = pixLeft[c] + pixUpper[c] - pixUpperLeft[c]; \
                if (prediction < 0) {                                    \
                    prediction = 0;                                      \
                } else if (prediction > maxColor[c]) {                   \
                    prediction = maxColor[c];                            \
                }                                                        \
                diff |= ((pixHere[c] - prediction) & maxColor[c])        \
                    << shiftBits[c];                                     \
            }                                                            \
            if (endianMismatch) {                                        \
                diff = Swap##bpp(diff);                                  \
            }                                                            \
            *buf++ = diff;                                               \
        }                                                                \
    }                                                                    \
}

DEFINE_GRADIENT_FILTER_FUNCTION(16)
DEFINE_GRADIENT_FILTER_FUNCTION(32)


/*
 * Code to guess if given rectangle is suitable for smooth image
 * compression (by applying "gradient" filter or JPEG coder).
 */

#define JPEG_MIN_RECT_SIZE  4096

#define DETECT_SUBROW_WIDTH    7
#define DETECT_MIN_WIDTH       8
#define DETECT_MIN_HEIGHT      8

static int
DetectSmoothImage (fmt, w, h)
    rfbPixelFormat *fmt;
    int w, h;
{
    unsigned long avgError;

    if ( rfbServerFormat.bitsPerPixel == 8 || fmt->bitsPerPixel == 8 ||
         w < DETECT_MIN_WIDTH || h < DETECT_MIN_HEIGHT ) {
        return 0;
    }

    if (qualityLevel != -1) {
        if (w * h < JPEG_MIN_RECT_SIZE) {
            return 0;
        }
    } else {
        if ( rfbTightDisableGradient ||
             w * h < tightConf[compressLevel].gradientMinRectSize ) {
            return 0;
        }
    }

    if (fmt->bitsPerPixel == 32) {
        if (usePixelFormat24) {
            avgError = DetectSmoothImage24(fmt, w, h);
            if (qualityLevel != -1) {
                return (avgError < tightConf[qualityLevel].jpegThreshold24);
            }
            return (avgError < tightConf[compressLevel].gradientThreshold24);
        } else {
            avgError = DetectSmoothImage32(fmt, w, h);
        }
    } else {
        avgError = DetectSmoothImage16(fmt, w, h);
    }
    if (qualityLevel != -1) {
        return (avgError < tightConf[qualityLevel].jpegThreshold);
    }
    return (avgError < tightConf[compressLevel].gradientThreshold);
}

static unsigned long
DetectSmoothImage24 (fmt, w, h)
    rfbPixelFormat *fmt;
    int w, h;
{
    int off;
    int x, y, d, dx, c;
    int diffStat[256];
    int pixelCount = 0;
    int pix, left[3];
    unsigned long avgError;

    /* If client is big-endian, color samples begin from the second
       byte (offset 1) of a 32-bit pixel value. */
    off = (fmt->bigEndian != 0);

    memset(diffStat, 0, 256*sizeof(int));

    y = 0, x = 0;
    while (y < h && x < w) {
        for (d = 0; d < h - y && d < w - x - DETECT_SUBROW_WIDTH; d++) {
            for (c = 0; c < 3; c++) {
                left[c] = (int)tightBeforeBuf[((y+d)*w+x+d)*4+off+c] & 0xFF;
            }
            for (dx = 1; dx <= DETECT_SUBROW_WIDTH; dx++) {
                for (c = 0; c < 3; c++) {
                    pix = (int)tightBeforeBuf[((y+d)*w+x+d+dx)*4+off+c] & 0xFF;
                    diffStat[abs(pix - left[c])]++;
                    left[c] = pix;
                }
                pixelCount++;
            }
        }
        if (w > h) {
            x += h;
            y = 0;
        } else {
            x = 0;
            y += w;
        }
    }

    if (diffStat[0] * 33 / pixelCount >= 95)
        return 0;

    avgError = 0;
    for (c = 1; c < 8; c++) {
        avgError += (unsigned long)diffStat[c] * (unsigned long)(c * c);
        if (diffStat[c] == 0 || diffStat[c] > diffStat[c-1] * 2)
            return 0;
    }
    for (; c < 256; c++) {
        avgError += (unsigned long)diffStat[c] * (unsigned long)(c * c);
    }
    avgError /= (pixelCount * 3 - diffStat[0]);

    return avgError;
}

#define DEFINE_DETECT_FUNCTION(bpp)                                          \
                                                                             \
static unsigned long                                                         \
DetectSmoothImage##bpp (fmt, w, h)                                           \
    rfbPixelFormat *fmt;                                                     \
    int w, h;                                                                \
{                                                                            \
    Bool endianMismatch;                                                     \
    CARD##bpp pix;                                                           \
    int maxColor[3], shiftBits[3];                                           \
    int x, y, d, dx, c;                                                      \
    int diffStat[256];                                                       \
    int pixelCount = 0;                                                      \
    int sample, sum, left[3];                                                \
    unsigned long avgError;                                                  \
                                                                             \
    endianMismatch = (!rfbServerFormat.bigEndian != !fmt->bigEndian);        \
                                                                             \
    maxColor[0] = fmt->redMax;                                               \
    maxColor[1] = fmt->greenMax;                                             \
    maxColor[2] = fmt->blueMax;                                              \
    shiftBits[0] = fmt->redShift;                                            \
    shiftBits[1] = fmt->greenShift;                                          \
    shiftBits[2] = fmt->blueShift;                                           \
                                                                             \
    memset(diffStat, 0, 256*sizeof(int));                                    \
                                                                             \
    y = 0, x = 0;                                                            \
    while (y < h && x < w) {                                                 \
        for (d = 0; d < h - y && d < w - x - DETECT_SUBROW_WIDTH; d++) {     \
            pix = ((CARD##bpp *)tightBeforeBuf)[(y+d)*w+x+d];                \
            if (endianMismatch) {                                            \
                pix = Swap##bpp(pix);                                        \
            }                                                                \
            for (c = 0; c < 3; c++) {                                        \
                left[c] = (int)(pix >> shiftBits[c] & maxColor[c]);          \
            }                                                                \
            for (dx = 1; dx <= DETECT_SUBROW_WIDTH; dx++) {                  \
                pix = ((CARD##bpp *)tightBeforeBuf)[(y+d)*w+x+d+dx];         \
                if (endianMismatch) {                                        \
                    pix = Swap##bpp(pix);                                    \
                }                                                            \
                sum = 0;                                                     \
                for (c = 0; c < 3; c++) {                                    \
                    sample = (int)(pix >> shiftBits[c] & maxColor[c]);       \
                    sum += abs(sample - left[c]);                            \
                    left[c] = sample;                                        \
                }                                                            \
                if (sum > 255)                                               \
                    sum = 255;                                               \
                diffStat[sum]++;                                             \
                pixelCount++;                                                \
            }                                                                \
        }                                                                    \
        if (w > h) {                                                         \
            x += h;                                                          \
            y = 0;                                                           \
        } else {                                                             \
            x = 0;                                                           \
            y += w;                                                          \
        }                                                                    \
    }                                                                        \
                                                                             \
    if ((diffStat[0] + diffStat[1]) * 100 / pixelCount >= 90)                \
        return 0;                                                            \
                                                                             \
    avgError = 0;                                                            \
    for (c = 1; c < 8; c++) {                                                \
        avgError += (unsigned long)diffStat[c] * (unsigned long)(c * c);     \
        if (diffStat[c] == 0 || diffStat[c] > diffStat[c-1] * 2)             \
            return 0;                                                        \
    }                                                                        \
    for (; c < 256; c++) {                                                   \
        avgError += (unsigned long)diffStat[c] * (unsigned long)(c * c);     \
    }                                                                        \
    avgError /= (pixelCount - diffStat[0]);                                  \
                                                                             \
    return avgError;                                                         \
}

DEFINE_DETECT_FUNCTION(16)
DEFINE_DETECT_FUNCTION(32)


/*
 * JPEG compression stuff.
 */

static struct jpeg_destination_mgr jpegDstManager;
static Bool jpegError;
static int jpegDstDataLen;

static Bool
SendJpegRect(cl, x, y, w, h, quality)
    rfbClientPtr cl;
    int x, y, w, h;
    int quality;
{
    struct jpeg_compress_struct cinfo;
    struct jpeg_error_mgr jerr;
    CARD8 *srcBuf;
    JSAMPROW rowPointer[1];
    int dy;

    if (rfbServerFormat.bitsPerPixel == 8)
        return SendFullColorRect(cl, w, h);

    srcBuf = (CARD8 *)xalloc(w * 3);
    if (srcBuf == NULL) {
        return SendFullColorRect(cl, w, h);
    }
    rowPointer[0] = srcBuf;

    cinfo.err = jpeg_std_error(&jerr);
    jpeg_create_compress(&cinfo);

    cinfo.image_width = w;
    cinfo.image_height = h;
    cinfo.input_components = 3;
    cinfo.in_color_space = JCS_RGB;

    jpeg_set_defaults(&cinfo);
    jpeg_set_quality(&cinfo, quality, TRUE);

    JpegSetDstManager (&cinfo);

    jpeg_start_compress(&cinfo, TRUE);

    for (dy = 0; dy < h; dy++) {
        PrepareRowForJpeg(srcBuf, x, y + dy, w);
        jpeg_write_scanlines(&cinfo, rowPointer, 1);
        if (jpegError)
            break;
    }

    if (!jpegError)
        jpeg_finish_compress(&cinfo);

    jpeg_destroy_compress(&cinfo);
    xfree((char *)srcBuf);

    if (jpegError)
        return SendFullColorRect(cl, w, h);

    if (ublen + TIGHT_MIN_TO_COMPRESS + 1 > UPDATE_BUF_SIZE) {
        if (!rfbSendUpdateBuf(cl))
            return FALSE;
    }

    updateBuf[ublen++] = (char)(rfbTightJpeg << 4);
    cl->rfbBytesSent[rfbEncodingTight]++;

    return SendCompressedData(cl, jpegDstDataLen);
}

static void
PrepareRowForJpeg(dst, x, y, count)
    CARD8 *dst;
    int x, y, count;
{
    if (rfbServerFormat.bitsPerPixel == 32) {
        if ( rfbServerFormat.redMax == 0xFF &&
             rfbServerFormat.greenMax == 0xFF &&
             rfbServerFormat.blueMax == 0xFF ) {
            PrepareRowForJpeg24(dst, x, y, count);
        } else {
            PrepareRowForJpeg32(dst, x, y, count);
        }
    } else {
        /* 16 bpp assumed. */
        PrepareRowForJpeg16(dst, x, y, count);
    }
}

static void
PrepareRowForJpeg24(dst, x, y, count)
    CARD8 *dst;
    int x, y, count;
{
    CARD32 *fbptr;
    CARD32 pix;

    fbptr = (CARD32 *)
        &rfbScreen.pfbMemory[y * rfbScreen.paddedWidthInBytes + x * 4];

    while (count--) {
        pix = *fbptr++;
        *dst++ = (CARD8)(pix >> rfbServerFormat.redShift);
        *dst++ = (CARD8)(pix >> rfbServerFormat.greenShift);
        *dst++ = (CARD8)(pix >> rfbServerFormat.blueShift);
    }
}

#define DEFINE_JPEG_GET_ROW_FUNCTION(bpp)                                   \
                                                                            \
static void                                                                 \
PrepareRowForJpeg##bpp(dst, x, y, count)                                    \
    CARD8 *dst;                                                             \
    int x, y, count;                                                        \
{                                                                           \
    CARD##bpp *fbptr;                                                       \
    CARD##bpp pix;                                                          \
    int inRed, inGreen, inBlue;                                             \
                                                                            \
    fbptr = (CARD##bpp *)                                                   \
        &rfbScreen.pfbMemory[y * rfbScreen.paddedWidthInBytes +             \
                             x * (bpp / 8)];                                \
                                                                            \
    while (count--) {