GUAC-240: Approximate whether images will compress well with JPEG vs. PNG.

src/common/Makefile.am

@@ -35,8 +35,7 @@ noinst_HEADERS =            \
     guac_pointer_cursor.h   \
     guac_rect.h             \
     guac_string.h           \
-    guac_surface.h          \
+    guac_surface.h
-    guac_surface_smoothness.h
 
 libguac_common_la_SOURCES =   \
     guac_io.c                 \
@@ -48,8 +47,7 @@ libguac_common_la_SOURCES =   \
     guac_pointer_cursor.c     \
     guac_rect.c               \
     guac_string.c             \
-    guac_surface.c            \
+    guac_surface.c
-    guac_surface_smoothness.c
 
 libguac_common_la_CFLAGS =  \
     -Werror -Wall -pedantic \

src/common/guac_surface.c

@@ -23,7 +23,6 @@
 #include "config.h"
 #include "guac_rect.h"
 #include "guac_surface.h"
-#include "guac_surface_smoothness.h"
 
 #include <cairo/cairo.h>
 #include <guacamole/client.h>
@@ -313,6 +312,70 @@ static unsigned int __guac_common_surface_calculate_framerate(
 
     return 0;
 
+}
+
+ /**
+ * Guesses whether a rectangle within a particular surface would be better
+ * compressed as PNG or as JPEG. Positive values indicate PNG is likely to
+ * be superior, while negative values indicate JPEG.
+ *
+ * @param surface
+ *     The surface containing the image data to check.
+ *
+ * @param rect
+ *     The rect to check within the given surface.
+ *
+ * @return
+ *     Positive values if PNG compression is likely to perform better than
+ *     JPEG, or negative values if JPEG is likely to perform better than PNG.
+ */
+static int guac_common_surface_png_optimality(guac_common_surface* surface,
+        const guac_common_rect* rect) {
+
+    int x, y;
+
+    int similarity = 0;
+
+    /* Get image/buffer metrics */
+    int width = rect->width;
+    int height = rect->height;
+    int stride = surface->stride;
+
+    /* Get buffer from surface */
+    unsigned char* buffer = surface->buffer + rect->y * stride + rect->x * 4;
+
+    /* For each row */
+    for (y = 0; y < height; y++) {
+
+        uint32_t last_pixel = -1;
+        uint32_t* row = (uint32_t*) buffer;
+
+        /* For each pixel in current row */
+        for (x = 0; x < width; x++) {
+
+            /* Get next pixel */
+            uint32_t current_pixel = *(row++);
+
+            /* Update similarity according to whether pixel is identical */
+            if (last_pixel != -1) {
+                if (current_pixel == last_pixel)
+                    similarity++;
+                else
+                    similarity--;
+            }
+
+            last_pixel = current_pixel;
+
+        }
+
+        /* Advance to next row */
+        buffer += stride;
+
+    }
+
+    /* Return rough approximation of optimality for PNG compression */
+    return 0xFF * similarity / width / height;
+
 }
 
 /**
@@ -336,7 +399,8 @@ static int __guac_common_surface_should_use_jpeg(guac_common_surface* surface,
     int framerate = __guac_common_surface_calculate_framerate(surface, rect);
 
     /* JPEG is preferred if framerate is high enough */
-    return framerate >= GUAC_COMMON_SURFACE_JPEG_FRAMERATE;
+    return framerate >= GUAC_COMMON_SURFACE_JPEG_FRAMERATE
+        && guac_common_surface_png_optimality(surface, rect) < 0;
 
 }
 

src/common/guac_surface_smoothness.c

@@ -1,158 +0,0 @@
-/*
- * Copyright (C) 2015 Glyptodon LLC
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-/*
- * Smoothness detection from:
- * QEMU VNC display driver: tight encoding
- *
- * From libvncserver/libvncserver/tight.c
- * Copyright (C) 2000, 2001 Const Kaplinsky.  All Rights Reserved.
- * Copyright (C) 1999 AT&T Laboratories Cambridge.  All Rights Reserved.
- *
- * Copyright (C) 2010 Corentin Chary <corentin.chary@gmail.com>
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
- * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-#include "guac_surface_smoothness.h"
-
-#include <stdlib.h>
-#include <stdint.h>
-#include <string.h>
-
-/**
- * The threshold to determine an image to be smooth.
- */
-#define GUAC_SURFACE_SMOOTHNESS_THRESHOLD 0
-
-/**
- * Width of sub-row when detecting image smoothness.
- */
-#define GUAC_SURFACE_SMOOTHNESS_DETECT_SUBROW_WIDTH 7
-
-int guac_common_surface_rect_is_smooth(guac_common_surface* surface,
-        guac_common_rect* rect)
-{
-
-    /*
-     * Code to guess if the image in a given rectangle is smooth
-     * (by applying "gradient" filter or JPEG coder).
-     */
-    int x, y, d, dx;
-    unsigned int c;
-    unsigned int stats[256];
-    int pixels = 0;
-    int pix, left[3];
-    unsigned char* buffer = surface->buffer;
-    int stride = surface->stride;
-    int w = rect->x + rect->width;
-    int h = rect->y + rect->height;
-
-    /* If rect is out of bounds, bail out */
-    if (rect->x < 0 || rect->y < 0 ||
-        w > surface->width || h > surface->height) {
-        return 0;
-    }
-
-    /* If rect is too small to process, bail out */
-    if (rect->width < GUAC_SURFACE_SMOOTHNESS_DETECT_SUBROW_WIDTH + 1 ||
-        rect->height < GUAC_SURFACE_SMOOTHNESS_DETECT_SUBROW_WIDTH + 1) {
-        return 0;
-    }
-
-    /* Init stats array */
-    memset(stats, 0, sizeof (stats));
-
-    for (y = rect->y, x = rect->x; y < h && x < w;) {
-
-        /* Scan sub-sections of the surface to determine how close the colors are
-         * to the previous. */
-        for (d = 0;
-             d < h - y && d < w - x - GUAC_SURFACE_SMOOTHNESS_DETECT_SUBROW_WIDTH;
-             d++) {
-
-            for (c = 0; c < 3; c++) {
-                unsigned int index = (y+d)*stride + (x+d)*4 + c;
-                left[c] = buffer[index] & 0xFF;
-            }
-
-            for (dx = 1; dx <= GUAC_SURFACE_SMOOTHNESS_DETECT_SUBROW_WIDTH; dx++) {
-
-                for (c = 0; c < 3; c++) {
-                    unsigned int index = (y+d)*stride + (x+d+dx)*4 + c;
-                    pix = buffer[index] & 0xFF;
-                    stats[abs(pix - left[c])]++;
-                    left[c] = pix;
-                }
-                ++pixels;
-            }
-        }
-
-        /* Advance to next section */
-        if (w > h) {
-            x += h;
-            y = rect->y;
-        } else {
-            x = rect->x;
-            y += w;
-        }
-    }
-
-    if (pixels == 0) {
-        return 1;
-    }
-
-    /* 95% smooth or more */
-    if (stats[0] * 33 / pixels >= 95) {
-        return 1;
-    }
-
-    unsigned int smoothness = 0;
-    for (c = 1; c < 8; c++) {
-        smoothness += stats[c] * (c * c);
-        if (stats[c] == 0 || stats[c] > stats[c-1] * 2) {
-            return 1;
-        }
-    }
-    for (; c < 256; c++) {
-        smoothness += stats[c] * (c * c);
-    }
-    smoothness /= (pixels * 3 - stats[0]);
-
-    return smoothness <= GUAC_SURFACE_SMOOTHNESS_THRESHOLD;
-}

src/common/guac_surface_smoothness.h

@@ -1,43 +0,0 @@
-/*
- * Copyright (C) 2015 Glyptodon LLC
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-#ifndef __GUAC_COMMON_SURFACE_SMOOTHNESS_H
-#define __GUAC_COMMON_SURFACE_SMOOTHNESS_H
-
-#include "guac_surface.h"
-
-/**
- * Returns the smoothness of an area on a surface.
- *
- * @param surface
- *     The surface on which the rectangle exists.
- *
- * @param rect
- *     The rectangle to check for smoothness.
- *
- * @return
- *     1 if rectangle is smooth, zero if not.
- */
-int guac_common_surface_rect_is_smooth(guac_common_surface* surface,
-        guac_common_rect* rect);
-
-#endif