vnc: tight: add JPEG and gradient subencoding with smooth image detection

Add gradient filter and JPEG compression with an heuristic to detect how
lossy the comppression will be. This code has been adapted from
libvncserver/tight.c.

JPEG support can be enabled/disabled at compile time with --enable-vnc-jpeg
and --disable-vnc-jpeg.

Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 558 insertions, 1 deletions

diff --git a/vnc-encoding-tight.c b/vnc-encoding-tight.c
index faba483..5b69ff0 100644
--- a/vnc-encoding-tight.c
+++ b/vnc-encoding-tight.c
@@ -26,6 +26,14 @@
  * THE SOFTWARE.
  */
 
+#include "qemu-common.h"
+
+#ifdef CONFIG_VNC_JPEG
+#include <stdio.h>
+#include <jpeglib.h>
+#endif
+
+#include "bswap.h"
 #include "qdict.h"
 #include "qint.h"
 #include "vnc.h"
@@ -56,6 +64,206 @@ static const struct {
 };
 
 /*
+ * Code to guess if given rectangle is suitable for smooth image
+ * compression (by applying "gradient" filter or JPEG coder).
+ */
+
+static uint
+tight_detect_smooth_image24(VncState *vs, int w, int h)
+{
+    int off;
+    int x, y, d, dx;
+    uint c;
+    uint stats[256];
+    int pixels = 0;
+    int pix, left[3];
+    uint errors;
+    unsigned char *buf = vs->tight.buffer;
+
+    /*
+     * If client is big-endian, color samples begin from the second
+     * byte (offset 1) of a 32-bit pixel value.
+     */
+    off = !!(vs->clientds.flags & QEMU_BIG_ENDIAN_FLAG);
+
+    memset(stats, 0, sizeof (stats));
+
+    for (y = 0, x = 0; y < h && x < w;) {
+        for (d = 0; d < h - y && d < w - x - VNC_TIGHT_DETECT_SUBROW_WIDTH;
+             d++) {
+            for (c = 0; c < 3; c++) {
+                left[c] = buf[((y+d)*w+x+d)*4+off+c] & 0xFF;
+            }
+            for (dx = 1; dx <= VNC_TIGHT_DETECT_SUBROW_WIDTH; dx++) {
+                for (c = 0; c < 3; c++) {
+                    pix = buf[((y+d)*w+x+d+dx)*4+off+c] & 0xFF;
+                    stats[abs(pix - left[c])]++;
+                    left[c] = pix;
+                }
+                pixels++;
+            }
+        }
+        if (w > h) {
+            x += h;
+            y = 0;
+        } else {
+            x = 0;
+            y += w;
+        }
+    }
+
+    /* 95% smooth or more ... */
+    if (stats[0] * 33 / pixels >= 95) {
+        return 0;
+    }
+
+    errors = 0;
+    for (c = 1; c < 8; c++) {
+        errors += stats[c] * (c * c);
+        if (stats[c] == 0 || stats[c] > stats[c-1] * 2) {
+            return 0;
+        }
+    }
+    for (; c < 256; c++) {
+        errors += stats[c] * (c * c);
+    }
+    errors /= (pixels * 3 - stats[0]);
+
+    return errors;
+}
+
+#define DEFINE_DETECT_FUNCTION(bpp)                                     \
+                                                                        \
+    static uint                                                         \
+    tight_detect_smooth_image##bpp(VncState *vs, int w, int h) {        \
+        bool endian;                                                    \
+        uint##bpp##_t pix;                                              \
+        int max[3], shift[3];                                           \
+        int x, y, d, dx;                                                \
+        uint c;                                                         \
+        uint stats[256];                                                \
+        int pixels = 0;                                                 \
+        int sample, sum, left[3];                                       \
+        uint errors;                                                    \
+        unsigned char *buf = vs->tight.buffer;                          \
+                                                                        \
+        endian = ((vs->clientds.flags & QEMU_BIG_ENDIAN_FLAG) !=        \
+                  (vs->ds->surface->flags & QEMU_BIG_ENDIAN_FLAG));     \
+                                                                        \
+                                                                        \
+        max[0] = vs->clientds.pf.rmax;                                  \
+        max[1] = vs->clientds.pf.gmax;                                  \
+        max[2] = vs->clientds.pf.bmax;                                  \
+        shift[0] = vs->clientds.pf.rshift;                              \
+        shift[1] = vs->clientds.pf.gshift;                              \
+        shift[2] = vs->clientds.pf.bshift;                              \
+                                                                        \
+        memset(stats, 0, sizeof(stats));                                \
+                                                                        \
+        y = 0, x = 0;                                                   \
+        while (y < h && x < w) {                                        \
+            for (d = 0; d < h - y &&                                    \
+                     d < w - x - VNC_TIGHT_DETECT_SUBROW_WIDTH; d++) {  \
+                pix = ((uint##bpp##_t *)buf)[(y+d)*w+x+d];              \
+                if (endian) {                                           \
+                    pix = bswap_##bpp(pix);                             \
+                }                                                       \
+                for (c = 0; c < 3; c++) {                               \
+                    left[c] = (int)(pix >> shift[c] & max[c]);          \
+                }                                                       \
+                for (dx = 1; dx <= VNC_TIGHT_DETECT_SUBROW_WIDTH;       \
+                     dx++) {                                            \
+                    pix = ((uint##bpp##_t *)buf)[(y+d)*w+x+d+dx];       \
+                    if (endian) {                                       \
+                        pix = bswap_##bpp(pix);                         \
+                    }                                                   \
+                    sum = 0;                                            \
+                    for (c = 0; c < 3; c++) {                           \
+                        sample = (int)(pix >> shift[c] & max[c]);       \
+                        sum += abs(sample - left[c]);                   \
+                        left[c] = sample;                               \
+                    }                                                   \
+                    if (sum > 255) {                                    \
+                        sum = 255;                                      \
+                    }                                                   \
+                    stats[sum]++;                                       \
+                    pixels++;                                           \
+                }                                                       \
+            }                                                           \
+            if (w > h) {                                                \
+                x += h;                                                 \
+                y = 0;                                                  \
+            } else {                                                    \
+                x = 0;                                                  \
+                y += w;                                                 \
+            }                                                           \
+        }                                                               \
+                                                                        \
+        if ((stats[0] + stats[1]) * 100 / pixels >= 90) {               \
+            return 0;                                                   \
+        }                                                               \
+                                                                        \
+        errors = 0;                                                     \
+        for (c = 1; c < 8; c++) {                                       \
+            errors += stats[c] * (c * c);                               \
+            if (stats[c] == 0 || stats[c] > stats[c-1] * 2) {           \
+                return 0;                                               \
+            }                                                           \
+        }                                                               \
+        for (; c < 256; c++) {                                          \
+            errors += stats[c] * (c * c);                               \
+        }                                                               \
+        errors /= (pixels - stats[0]);                                  \
+                                                                        \
+        return errors;                                                  \
+    }
+
+DEFINE_DETECT_FUNCTION(16)
+DEFINE_DETECT_FUNCTION(32)
+
+static int
+tight_detect_smooth_image(VncState *vs, int w, int h)
+{
+    uint errors;
+    int compression = vs->tight_compression;
+    int quality = vs->tight_quality;
+
+    if (ds_get_bytes_per_pixel(vs->ds) == 1 ||
+        vs->clientds.pf.bytes_per_pixel == 1 ||
+        w < VNC_TIGHT_DETECT_MIN_WIDTH || h < VNC_TIGHT_DETECT_MIN_HEIGHT) {
+        return 0;
+    }
+
+    if (vs->tight_quality != -1) {
+        if (w * h < VNC_TIGHT_JPEG_MIN_RECT_SIZE) {
+            return 0;
+        }
+    } else {
+        if (w * h < tight_conf[compression].gradient_min_rect_size) {
+            return 0;
+        }
+    }
+
+    if (vs->clientds.pf.bytes_per_pixel == 4) {
+        if (vs->tight_pixel24) {
+            errors = tight_detect_smooth_image24(vs, w, h);
+            if (vs->tight_quality != -1) {
+                return (errors < tight_conf[quality].jpeg_threshold24);
+            }
+            return (errors < tight_conf[compression].gradient_threshold24);
+        } else {
+            errors = tight_detect_smooth_image32(vs, w, h);
+        }
+    } else {
+        errors = tight_detect_smooth_image16(vs, w, h);
+    }
+    if (quality != -1) {
+        return (errors < tight_conf[quality].jpeg_threshold);
+    }
+    return (errors < tight_conf[compression].gradient_threshold);
+}
+
+/*
  * Code to determine how many different colors used in rectangle.
  */
 
@@ -335,6 +543,133 @@ DEFINE_MONO_ENCODE_FUNCTION(16)
 DEFINE_MONO_ENCODE_FUNCTION(32)
 
 /*
+ * ``Gradient'' filter for 24-bit color samples.
+ * Should be called only when redMax, greenMax and blueMax are 255.
+ * Color components assumed to be byte-aligned.
+ */
+
+static void
+tight_filter_gradient24(VncState *vs, uint8_t *buf, int w, int h)
+{
+    uint32_t *buf32;
+    uint32_t pix32;
+    int shift[3];
+    int *prev;
+    int here[3], upper[3], left[3], upperleft[3];
+    int prediction;
+    int x, y, c;
+
+    buf32 = (uint32_t *)buf;
+    memset(vs->tight_gradient.buffer, 0, w * 3 * sizeof(int));
+
+    if ((vs->clientds.flags & QEMU_BIG_ENDIAN_FLAG) ==
+        (vs->ds->surface->flags & QEMU_BIG_ENDIAN_FLAG)) {
+        shift[0] = vs->clientds.pf.rshift;
+        shift[1] = vs->clientds.pf.gshift;
+        shift[2] = vs->clientds.pf.bshift;
+    } else {
+        shift[0] = 24 - vs->clientds.pf.rshift;
+        shift[1] = 24 - vs->clientds.pf.gshift;
+        shift[2] = 24 - vs->clientds.pf.bshift;
+    }
+
+    for (y = 0; y < h; y++) {
+        for (c = 0; c < 3; c++) {
+            upper[c] = 0;
+            here[c] = 0;
+        }
+        prev = (int *)vs->tight_gradient.buffer;
+        for (x = 0; x < w; x++) {
+            pix32 = *buf32++;
+            for (c = 0; c < 3; c++) {
+                upperleft[c] = upper[c];
+                left[c] = here[c];
+                upper[c] = *prev;
+                here[c] = (int)(pix32 >> shift[c] & 0xFF);
+                *prev++ = here[c];
+
+                prediction = left[c] + upper[c] - upperleft[c];
+                if (prediction < 0) {
+                    prediction = 0;
+                } else if (prediction > 0xFF) {
+                    prediction = 0xFF;
+                }
+                *buf++ = (char)(here[c] - prediction);
+            }
+        }
+    }
+}
+
+
+/*
+ * ``Gradient'' filter for other color depths.
+ */
+
+#define DEFINE_GRADIENT_FILTER_FUNCTION(bpp)                            \
+                                                                        \
+    static void                                                         \
+    tight_filter_gradient##bpp(VncState *vs, uint##bpp##_t *buf,        \
+                               int w, int h) {                          \
+        uint##bpp##_t pix, diff;                                        \
+        bool endian;                                                    \
+        int *prev;                                                      \
+        int max[3], shift[3];                                           \
+        int here[3], upper[3], left[3], upperleft[3];                   \
+        int prediction;                                                 \
+        int x, y, c;                                                    \
+                                                                        \
+        memset (vs->tight_gradient.buffer, 0, w * 3 * sizeof(int));     \
+                                                                        \
+        endian = ((vs->clientds.flags & QEMU_BIG_ENDIAN_FLAG) !=        \
+                  (vs->ds->surface->flags & QEMU_BIG_ENDIAN_FLAG));     \
+                                                                        \
+        max[0] = vs->clientds.pf.rmax;                                  \
+        max[1] = vs->clientds.pf.gmax;                                  \
+        max[2] = vs->clientds.pf.bmax;                                  \
+        shift[0] = vs->clientds.pf.rshift;                              \
+        shift[1] = vs->clientds.pf.gshift;                              \
+        shift[2] = vs->clientds.pf.bshift;                              \
+                                                                        \
+        for (y = 0; y < h; y++) {                                       \
+            for (c = 0; c < 3; c++) {                                   \
+                upper[c] = 0;                                           \
+                here[c] = 0;                                            \
+            }                                                           \
+            prev = (int *)vs->tight_gradient.buffer;                    \
+            for (x = 0; x < w; x++) {                                   \
+                pix = *buf;                                             \
+                if (endian) {                                           \
+                    pix = bswap_##bpp(pix);                             \
+                }                                                       \
+                diff = 0;                                               \
+                for (c = 0; c < 3; c++) {                               \
+                    upperleft[c] = upper[c];                            \
+                    left[c] = here[c];                                  \
+                    upper[c] = *prev;                                   \
+                    here[c] = (int)(pix >> shift[c] & max[c]);          \
+                    *prev++ = here[c];                                  \
+                                                                        \
+                    prediction = left[c] + upper[c] - upperleft[c];     \
+                    if (prediction < 0) {                               \
+                        prediction = 0;                                 \
+                    } else if (prediction > max[c]) {                   \
+                        prediction = max[c];                            \
+                    }                                                   \
+                    diff |= ((here[c] - prediction) & max[c])           \
+                        << shift[c];                                    \
+                }                                                       \
+                if (endian) {                                           \
+                    diff = bswap_##bpp(diff);                           \
+                }                                                       \
+                *buf++ = diff;                                          \
+            }                                                           \
+        }                                                               \
+    }
+
+DEFINE_GRADIENT_FILTER_FUNCTION(16)
+DEFINE_GRADIENT_FILTER_FUNCTION(32)
+
+/*
  * Check if a rectangle is all of the same color. If needSameColor is
  * set to non-zero, then also check that its color equals to the
  * *colorPtr value. The result is 1 if the test is successfull, and in
@@ -702,6 +1037,41 @@ static void write_palette(const char *key, QObject *obj, void *opaque)
     }
 }
 
+static bool send_gradient_rect(VncState *vs, int w, int h)
+{
+    int stream = 3;
+    int level = tight_conf[vs->tight_compression].gradient_zlib_level;
+    size_t bytes;
+
+    if (vs->clientds.pf.bytes_per_pixel == 1)
+        return send_full_color_rect(vs, w, h);
+
+    vnc_write_u8(vs, (stream | VNC_TIGHT_EXPLICIT_FILTER) << 4);
+    vnc_write_u8(vs, VNC_TIGHT_FILTER_GRADIENT);
+
+    buffer_reserve(&vs->tight_gradient, w * 3 * sizeof (int));
+
+    if (vs->tight_pixel24) {
+        tight_filter_gradient24(vs, vs->tight.buffer, w, h);
+        bytes = 3;
+    } else if (vs->clientds.pf.bytes_per_pixel == 4) {
+        tight_filter_gradient32(vs, (uint32_t *)vs->tight.buffer, w, h);
+        bytes = 4;
+    } else {
+        tight_filter_gradient16(vs, (uint16_t *)vs->tight.buffer, w, h);
+        bytes = 2;
+    }
+
+    buffer_reset(&vs->tight_gradient);
+
+    bytes = w * h * bytes;
+    vs->tight.offset = bytes;
+
+    bytes = tight_compress_data(vs, stream, bytes,
+                                level, Z_FILTERED);
+    return (bytes >= 0);
+}
+
 static int send_palette_rect(VncState *vs, int w, int h, struct QDict *palette)
 {
     int stream = 2;
@@ -756,6 +1126,164 @@ static int send_palette_rect(VncState *vs, int w, int h, struct QDict *palette)
     return (bytes >= 0);
 }
 
+/*
+ * JPEG compression stuff.
+ */
+#ifdef CONFIG_VNC_JPEG
+static void jpeg_prepare_row24(VncState *vs, uint8_t *dst, int x, int y,
+                                     int count)
+{
+    VncDisplay *vd = vs->vd;
+    uint32_t *fbptr;
+    uint32_t pix;
+
+    fbptr = (uint32_t *)(vd->server->data + y * ds_get_linesize(vs->ds) +
+                         x * ds_get_bytes_per_pixel(vs->ds));
+
+    while (count--) {
+        pix = *fbptr++;
+        *dst++ = (uint8_t)(pix >> vs->ds->surface->pf.rshift);
+        *dst++ = (uint8_t)(pix >> vs->ds->surface->pf.gshift);
+        *dst++ = (uint8_t)(pix >> vs->ds->surface->pf.bshift);
+    }
+}
+
+#define DEFINE_JPEG_GET_ROW_FUNCTION(bpp)                               \
+                                                                        \
+    static void                                                         \
+    jpeg_prepare_row##bpp(VncState *vs, uint8_t *dst,                   \
+                                int x, int y, int count)                \
+    {                                                                   \
+        VncDisplay *vd = vs->vd;                                        \
+        uint##bpp##_t *fbptr;                                           \
+        uint##bpp##_t pix;                                              \
+        int r, g, b;                                                    \
+                                                                        \
+        fbptr = (uint##bpp##_t *)                                       \
+            (vd->server->data + y * ds_get_linesize(vs->ds) +           \
+             x * ds_get_bytes_per_pixel(vs->ds));                       \
+                                                                        \
+        while (count--) {                                               \
+            pix = *fbptr++;                                             \
+                                                                        \
+            r = (int)((pix >> vs->ds->surface->pf.rshift)               \
+                      & vs->ds->surface->pf.rmax);                      \
+            g = (int)((pix >> vs->ds->surface->pf.gshift)               \
+                      & vs->ds->surface->pf.gmax);                      \
+            b = (int)((pix >> vs->ds->surface->pf.bshift)               \
+                      & vs->ds->surface->pf.bmax);                      \
+                                                                        \
+            *dst++ = (uint8_t)((r * 255 + vs->ds->surface->pf.rmax / 2) \
+                               / vs->ds->surface->pf.rmax);             \
+            *dst++ = (uint8_t)((g * 255 + vs->ds->surface->pf.gmax / 2) \
+                               / vs->ds->surface->pf.gmax);             \
+            *dst++ = (uint8_t)((b * 255 + vs->ds->surface->pf.bmax / 2) \
+                               / vs->ds->surface->pf.bmax);             \
+        }                                                               \
+    }
+
+DEFINE_JPEG_GET_ROW_FUNCTION(16)
+DEFINE_JPEG_GET_ROW_FUNCTION(32)
+
+static void jpeg_prepare_row(VncState *vs, uint8_t *dst, int x, int y,
+                                       int count)
+{
+    if (vs->tight_pixel24)
+        jpeg_prepare_row24(vs, dst, x, y, count);
+    else if (ds_get_bytes_per_pixel(vs->ds) == 4)
+        jpeg_prepare_row32(vs, dst, x, y, count);
+    else
+        jpeg_prepare_row16(vs, dst, x, y, count);
+}
+
+/*
+ * Destination manager implementation for JPEG library.
+ */
+
+/* This is called once per encoding */
+static void jpeg_init_destination(j_compress_ptr cinfo)
+{
+    VncState *vs = cinfo->client_data;
+    Buffer *buffer = &vs->tight_jpeg;
+
+    cinfo->dest->next_output_byte = (JOCTET *)buffer->buffer + buffer->offset;
+    cinfo->dest->free_in_buffer = (size_t)(buffer->capacity - buffer->offset);
+}
+
+/* This is called when we ran out of buffer (shouldn't happen!) */
+static boolean jpeg_empty_output_buffer(j_compress_ptr cinfo)
+{
+    VncState *vs = cinfo->client_data;
+    Buffer *buffer = &vs->tight_jpeg;
+
+    buffer->offset = buffer->capacity;
+    buffer_reserve(buffer, 2048);
+    jpeg_init_destination(cinfo);
+    return TRUE;
+}
+
+/* This is called when we are done processing data */
+static void jpeg_term_destination(j_compress_ptr cinfo)
+{
+    VncState *vs = cinfo->client_data;
+    Buffer *buffer = &vs->tight_jpeg;
+
+    buffer->offset = buffer->capacity - cinfo->dest->free_in_buffer;
+}
+
+static int send_jpeg_rect(VncState *vs, int x, int y, int w, int h, int quality)
+{
+    struct jpeg_compress_struct cinfo;
+    struct jpeg_error_mgr jerr;
+    struct jpeg_destination_mgr manager;
+    JSAMPROW row[1];
+    uint8_t *buf;
+    int dy;
+
+    if (ds_get_bytes_per_pixel(vs->ds) == 1)
+        return send_full_color_rect(vs, w, h);
+
+    buf = qemu_malloc(w * 3);
+    row[0] = buf;
+    buffer_reserve(&vs->tight_jpeg, 2048);
+
+    cinfo.err = jpeg_std_error(&jerr);
+    jpeg_create_compress(&cinfo);
+
+    cinfo.client_data = vs;
+    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);
+
+    manager.init_destination = jpeg_init_destination;
+    manager.empty_output_buffer = jpeg_empty_output_buffer;
+    manager.term_destination = jpeg_term_destination;
+    cinfo.dest = &manager;
+
+    jpeg_start_compress(&cinfo, true);
+
+    for (dy = 0; dy < h; dy++) {
+        jpeg_prepare_row(vs, buf, x, y + dy, w);
+        jpeg_write_scanlines(&cinfo, row, 1);
+    }
+
+    jpeg_finish_compress(&cinfo);
+    jpeg_destroy_compress(&cinfo);
+
+    vnc_write_u8(vs, VNC_TIGHT_JPEG << 4);
+
+    tight_send_compact_size(vs, vs->tight_jpeg.offset);
+    vnc_write(vs, vs->tight_jpeg.buffer, vs->tight_jpeg.offset);
+    buffer_reset(&vs->tight_jpeg);
+
+    return 1;
+}
+#endif /* CONFIG_VNC_JPEG */
+
 static void vnc_tight_start(VncState *vs)
 {
     buffer_reset(&vs->tight);
@@ -788,13 +1316,38 @@ static int send_sub_rect(VncState *vs, int x, int y, int w, int h)
     colors = tight_fill_palette(vs, x, y, w * h, &fg, &bg, &palette);
 
     if (colors == 0) {
-        ret = send_full_color_rect(vs, w, h);
+        if (tight_detect_smooth_image(vs, w, h)) {
+            if (vs->tight_quality == -1) {
+                ret = send_gradient_rect(vs, w, h);
+            } else {
+#ifdef CONFIG_VNC_JPEG
+                int quality = tight_conf[vs->tight_quality].jpeg_quality;
+
+                ret = send_jpeg_rect(vs, x, y, w, h, quality);
+#else
+                ret = send_full_color_rect(vs, w, h);
+#endif
+            }
+        } else {
+            ret = send_full_color_rect(vs, w, h);
+        }
     } else if (colors == 1) {
         ret = send_solid_rect(vs);
     } else if (colors == 2) {
         ret = send_mono_rect(vs, w, h, bg, fg);
     } else if (colors <= 256) {
+#ifdef CONFIG_VNC_JPEG
+        if (colors > 96 && vs->tight_quality != -1 && vs->tight_quality <= 3 &&
+            tight_detect_smooth_image(vs, w, h)) {
+            int quality = tight_conf[vs->tight_quality].jpeg_quality;
+
+            ret = send_jpeg_rect(vs, x, y, w, h, quality);
+        } else {
+            ret = send_palette_rect(vs, w, h, palette);
+        }
+#else
         ret = send_palette_rect(vs, w, h, palette);
+#endif
     }
     QDECREF(palette);
     return ret;
@@ -956,4 +1509,8 @@ void vnc_tight_clear(VncState *vs)
 
     buffer_free(&vs->tight);
     buffer_free(&vs->tight_zlib);
+    buffer_free(&vs->tight_gradient);
+#ifdef CONFIG_VNC_JPEG
+    buffer_free(&vs->tight_jpeg);
+#endif
 }