poppler/poppler-0.12.3-downscale.patch

diff --git a/poppler/CairoOutputDev.cc b/poppler/CairoOutputDev.cc
index 9a0f3be..42ac3a8 100644
--- a/poppler/CairoOutputDev.cc
+++ b/poppler/CairoOutputDev.cc
@@ -58,6 +58,7 @@
 #include <splash/SplashBitmap.h>
 #include "CairoOutputDev.h"
 #include "CairoFontEngine.h"
+#include "CairoRescaleBox.h"
 //------------------------------------------------------------------------
 
 // #define LOG_CAIRO
@@ -1331,6 +1332,82 @@ void CairoOutputDev::endMaskClip(GfxState *state) {
   clearSoftMask(state);
 }
 
+cairo_surface_t *CairoOutputDev::downscaleSurface(cairo_surface_t *orig_surface) {
+  cairo_surface_t *dest_surface;
+  unsigned char *dest_buffer;
+  int dest_stride;
+  unsigned char *orig_buffer;
+  int orig_width, orig_height;
+  int orig_stride;
+  GBool res;
+
+  if (printing)
+    return NULL;
+
+  cairo_matrix_t matrix;
+  cairo_get_matrix(cairo, &matrix);
+
+  /* this whole computation should be factored out */
+  double xScale = matrix.xx;
+  double yScale = matrix.yy;
+  int tx, tx2, ty, ty2; /* the integer co-oridinates of the resulting image */
+  int scaledHeight;
+  int scaledWidth;
+  if (xScale >= 0) {
+    tx = splashRound(matrix.x0 - 0.01);
+    tx2 = splashRound(matrix.x0 + xScale + 0.01) - 1;
+  } else {
+    tx = splashRound(matrix.x0 + 0.01) - 1;
+    tx2 = splashRound(matrix.x0 + xScale - 0.01);
+  }
+  scaledWidth = abs(tx2 - tx) + 1;
+  //scaledWidth = splashRound(fabs(xScale));
+  if (scaledWidth == 0) {
+    // technically, this should draw nothing, but it generally seems
+    // better to draw a one-pixel-wide stripe rather than throwing it
+    // away
+    scaledWidth = 1;
+  }
+  if (yScale >= 0) {
+    ty = splashFloor(matrix.y0 + 0.01);
+    ty2 = splashCeil(matrix.y0 + yScale - 0.01);
+  } else {
+    ty = splashCeil(matrix.y0 - 0.01);
+    ty2 = splashFloor(matrix.y0 + yScale + 0.01);
+  }
+  scaledHeight = abs(ty2 - ty);
+  if (scaledHeight == 0) {
+    scaledHeight = 1;
+  }
+
+  orig_width = cairo_image_surface_get_width (orig_surface);
+  orig_height = cairo_image_surface_get_height (orig_surface);
+  if (scaledWidth >= orig_width || scaledHeight >= orig_height)
+    return NULL;
+
+  dest_surface = cairo_surface_create_similar (orig_surface,
+					       cairo_surface_get_content (orig_surface),
+					       scaledWidth, scaledHeight);
+  dest_buffer = cairo_image_surface_get_data (dest_surface);
+  dest_stride = cairo_image_surface_get_stride (dest_surface);
+
+  orig_buffer = cairo_image_surface_get_data (orig_surface);
+  orig_stride = cairo_image_surface_get_stride (orig_surface);
+
+  res = downscale_box_filter((uint32_t *)orig_buffer,
+			     orig_stride, orig_width, orig_height,
+			     scaledWidth, scaledHeight, 0, 0,
+			     scaledWidth, scaledHeight,
+			     (uint32_t *)dest_buffer, dest_stride);
+  if (!res) {
+    cairo_surface_destroy (dest_surface);
+    return NULL;
+  }
+
+  return dest_surface;
+
+}
+
 void CairoOutputDev::drawImageMask(GfxState *state, Object *ref, Stream *str,
 				   int width, int height, GBool invert,
 				   GBool interpolate, GBool inlineImg) {
@@ -2094,6 +2171,18 @@ void CairoOutputDev::drawImage(GfxState *state, Object *ref, Stream *str,
   }
   gfree(lookup);
 
+  cairo_surface_t *scaled_surface;
+
+  scaled_surface = downscaleSurface (image);
+  if (scaled_surface) {
+    if (cairo_surface_status (scaled_surface))
+      goto cleanup;
+    cairo_surface_destroy (image);
+    image = scaled_surface;
+    width = cairo_image_surface_get_width (image);
+    height = cairo_image_surface_get_height (image);
+  }
+
   cairo_surface_mark_dirty (image);
   pattern = cairo_pattern_create_for_surface (image);
   cairo_surface_destroy (image);
diff --git a/poppler/CairoOutputDev.h b/poppler/CairoOutputDev.h
index fb9c0d7..266f0cb 100644
--- a/poppler/CairoOutputDev.h
+++ b/poppler/CairoOutputDev.h
@@ -268,6 +268,7 @@ public:
 
 protected:
   void doPath(cairo_t *cairo, GfxState *state, GfxPath *path);
+  cairo_surface_t *downscaleSurface(cairo_surface_t *orig_surface);
   
   GfxRGB fill_color, stroke_color;
   cairo_pattern_t *fill_pattern, *stroke_pattern;
diff --git a/poppler/CairoRescaleBox.cc b/poppler/CairoRescaleBox.cc
new file mode 100644
index 0000000..dce5ddd
--- /dev/null
+++ b/poppler/CairoRescaleBox.cc
@@ -0,0 +1,352 @@
+/* -*- Mode: c; c-basic-offset: 4; tab-width: 8; indent-tabs-mode: t; -*- */
+/*
+ * Copyright © 2009 Mozilla Corporation
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that
+ * copyright notice and this permission notice appear in supporting
+ * documentation, and that the name of Mozilla Corporation not be used in
+ * advertising or publicity pertaining to distribution of the software without
+ * specific, written prior permission.  Mozilla Corporation makes no
+ * representations about the suitability of this software for any purpose.  It
+ * is provided "as is" without express or implied warranty.
+ *
+ * MOZILLA CORPORATION DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT
+ * SHALL MOZILLA CORPORATION BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ *
+ * Author: Jeff Muizelaar, Mozilla Corp.
+ */
+
+/* This implements a box filter that supports non-integer box sizes */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <stdint.h>
+#include <stdio.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <math.h>
+#include "goo/gmem.h"
+#include "CairoRescaleBox.h"
+
+typedef unsigned short int      uint16_t;
+typedef unsigned int            uint32_t;
+
+/* we work in fixed point where 1. == 1 << 24 */
+#define FIXED_SHIFT 24
+
+static void downsample_row_box_filter (
+        int start, int width,
+        uint32_t *src, uint32_t *dest,
+        int coverage[], int pixel_coverage)
+{
+    /* we need an array of the pixel contribution of each destination pixel on the boundaries.
+     * we invert the value to get the value on the other size of the box */
+    /*
+
+       value  = a * contribution * 1/box_size
+       value += a * 1/box_size
+       value += a * 1/box_size
+       value += a * 1/box_size
+       value += a * (1 - contribution) * 1/box_size
+                a * (1/box_size - contribution * 1/box_size)
+
+        box size is constant
+
+
+       value = a * contribtion_a * 1/box_size + b * contribution_b * 1/box_size
+               contribution_b = (1 - contribution_a)
+                              = (1 - contribution_a_next)
+    */
+
+    /* box size = ceil(src_width/dest_width) */
+    int x = 0;
+
+    /* skip to start */
+    /* XXX: it might be possible to do this directly instead of iteratively, however
+     * the iterative solution is simple */
+    while (x < start)
+    {
+        int box = 1 << FIXED_SHIFT;
+        int start_coverage = coverage[x];
+        box -= start_coverage;
+        src++;
+        while (box >= pixel_coverage)
+        {
+            src++;
+            box -= pixel_coverage;
+        }
+        x++;
+    }
+
+    while (x < start + width)
+    {
+        uint32_t a = 0;
+        uint32_t r = 0;
+        uint32_t g = 0;
+        uint32_t b = 0;
+        int box = 1 << FIXED_SHIFT;
+        int start_coverage = coverage[x];
+
+        a = ((*src >> 24) & 0xff) * start_coverage;
+        r = ((*src >> 16) & 0xff) * start_coverage;
+        g = ((*src >>  8) & 0xff) * start_coverage;
+        b = ((*src >>  0) & 0xff) * start_coverage;
+        src++;
+        x++;
+        box -= start_coverage;
+
+        while (box >= pixel_coverage)
+        {
+            a += ((*src >> 24) & 0xff) * pixel_coverage;
+            r += ((*src >> 16) & 0xff) * pixel_coverage;
+            g += ((*src >>  8) & 0xff) * pixel_coverage;
+            b += ((*src >>  0) & 0xff) * pixel_coverage;
+            src++;
+
+            box -= pixel_coverage;
+        }
+
+        /* multiply by whatever is leftover
+         * this ensures that we don't bias down.
+         * i.e. start_coverage + n*pixel_coverage + box == 1 << 24 */
+        if (box > 0)
+        {
+            a += ((*src >> 24) & 0xff) * box;
+            r += ((*src >> 16) & 0xff) * box;
+            g += ((*src >>  8) & 0xff) * box;
+            b += ((*src >>  0) & 0xff) * box;
+        }
+
+        a >>= FIXED_SHIFT;
+        r >>= FIXED_SHIFT;
+        g >>= FIXED_SHIFT;
+        b >>= FIXED_SHIFT;
+
+        *dest = (a << 24) | (r << 16) | (g << 8) | b;
+        dest++;
+    }
+}
+
+static void downsample_columns_box_filter (
+        int n,
+        int start_coverage,
+        int pixel_coverage,
+        uint32_t *src, uint32_t *dest)
+{
+    int stride = n;
+    while (n--) {
+        uint32_t a = 0;
+        uint32_t r = 0;
+        uint32_t g = 0;
+        uint32_t b = 0;
+        uint32_t *column_src = src;
+        int box = 1 << FIXED_SHIFT;
+
+        a = ((*column_src >> 24) & 0xff) * start_coverage;
+        r = ((*column_src >> 16) & 0xff) * start_coverage;
+        g = ((*column_src >>  8) & 0xff) * start_coverage;
+        b = ((*column_src >>  0) & 0xff) * start_coverage;
+        column_src += stride;
+        box -= start_coverage;
+
+        while (box >= pixel_coverage)
+        {
+            a += ((*column_src >> 24) & 0xff) * pixel_coverage;
+            r += ((*column_src >> 16) & 0xff) * pixel_coverage;
+            g += ((*column_src >>  8) & 0xff) * pixel_coverage;
+            b += ((*column_src >>  0) & 0xff) * pixel_coverage;
+            column_src += stride;
+            box -= pixel_coverage;
+        }
+
+        if (box > 0) {
+            a += ((*column_src >> 24) & 0xff) * box;
+            r += ((*column_src >> 16) & 0xff) * box;
+            g += ((*column_src >>  8) & 0xff) * box;
+            b += ((*column_src >>  0) & 0xff) * box;
+        }
+
+        a >>= FIXED_SHIFT;
+        r >>= FIXED_SHIFT;
+        g >>= FIXED_SHIFT;
+        b >>= FIXED_SHIFT;
+
+        *dest = (a << 24) | (r << 16) | (g << 8) | b;
+        dest++;
+        src++;
+    }
+}
+
+static int compute_coverage (int coverage[], int src_length, int dest_length)
+{
+    int i;
+    /* num = src_length/dest_length
+       total = sum(pixel) / num
+
+       pixel * 1/num == pixel * dest_length / src_length
+    */
+    /* the average contribution of each source pixel */
+    int ratio = ((1 << 24)*(long long int)dest_length)/src_length;
+    /* because ((1 << 24)*(long long int)dest_length) won't always be divisible by src_length
+     * we'll need someplace to put the other bits.
+     *
+     * We want to ensure a + n*ratio < 1<<24
+     *
+     * 1<<24
+     * */
+
+    double scale = (double)src_length/dest_length;
+
+    /* for each destination pixel compute the coverage of the left most pixel included in the box */
+    /* I have a proof of this, which this margin is too narrow to contain */
+    for (i=0; i<dest_length; i++)
+    {
+        float left_side = i*scale;
+        float right_side = (i+1)*scale;
+        float right_fract = right_side - floor (right_side);
+        float left_fract = ceil (left_side) - left_side;
+        int overage;
+        /* find out how many source pixels will be used to fill the box */
+        int count = floor (right_side) - ceil (left_side);
+        /* what's the maximum value this expression can become?
+           floor((i+1)*scale) - ceil(i*scale)
+
+           (i+1)*scale - i*scale == scale
+
+           since floor((i+1)*scale) <= (i+1)*scale
+           and   ceil(i*scale)      >= i*scale
+
+           floor((i+1)*scale) - ceil(i*scale) <= scale
+
+           further since: floor((i+1)*scale) - ceil(i*scale) is an integer
+
+           therefore:
+           floor((i+1)*scale) - ceil(i*scale) <= floor(scale)
+        */
+
+        if (left_fract == 0.)
+            count--;
+
+        /* compute how much the right-most pixel contributes */
+        overage = ratio*(right_fract);
+
+        /* the remainder is the the amount that the left-most pixel
+         * contributes */
+        coverage[i] = (1<<24) - (count * ratio + overage);
+    }
+
+    return ratio;
+}
+
+GBool downscale_box_filter(uint32_t *orig, int orig_stride, unsigned orig_width, unsigned orig_height,
+			   signed scaled_width, signed scaled_height,
+			   uint16_t start_column, uint16_t start_row,
+			   uint16_t width, uint16_t height,
+			   uint32_t *dest, int dst_stride)
+{
+    int pixel_coverage_x, pixel_coverage_y;
+    int dest_y;
+    int src_y = 0;
+    uint32_t *scanline = orig;
+    int *x_coverage = NULL;
+    int *y_coverage = NULL;
+    uint32_t *temp_buf = NULL;
+    GBool retval = gFalse;
+
+    x_coverage = (int *)gmallocn3 (orig_width, 1, sizeof(int));
+    y_coverage = (int *)gmallocn3 (orig_height, 1, sizeof(int));
+
+    /* we need to allocate enough room for ceil(src_height/dest_height)+1
+      Example:
+      src_height = 140
+      dest_height = 50
+      src_height/dest_height = 2.8
+
+      |-------------|       2.8 pixels
+      |----|----|----|----| 4 pixels
+      need to sample 3 pixels
+
+         |-------------|       2.8 pixels
+      |----|----|----|----| 4 pixels
+      need to sample 4 pixels
+    */
+
+    temp_buf = (uint32_t *)gmallocn3 ((orig_height + scaled_height-1)/scaled_height+1, scaled_width, sizeof(uint32_t));
+
+    if (!x_coverage || !y_coverage || !scanline || !temp_buf)
+	goto cleanup;
+
+    pixel_coverage_x = compute_coverage (x_coverage, orig_width, scaled_width);
+    pixel_coverage_y = compute_coverage (y_coverage, orig_height, scaled_height);
+
+    assert (width + start_column <= scaled_width);
+
+    /* skip the rows at the beginning */
+    for (dest_y = 0; dest_y < start_row; dest_y++)
+    {
+        int box = 1 << FIXED_SHIFT;
+        int start_coverage_y = y_coverage[dest_y];
+        box -= start_coverage_y;
+        src_y++;
+        while (box >= pixel_coverage_y)
+        {
+            box -= pixel_coverage_y;
+            src_y++;
+        }
+    }
+
+    for (; dest_y < start_row + height; dest_y++)
+    {
+        int columns = 0;
+        int box = 1 << FIXED_SHIFT;
+        int start_coverage_y = y_coverage[dest_y];
+
+	scanline = orig + src_y * orig_stride / 4;
+        downsample_row_box_filter (start_column, width, scanline, temp_buf + width * columns, x_coverage, pixel_coverage_x);
+        columns++;
+        src_y++;
+        box -= start_coverage_y;
+
+        while (box >= pixel_coverage_y)
+        {
+	    scanline = orig + src_y * orig_stride / 4;
+            downsample_row_box_filter (start_column, width, scanline, temp_buf + width * columns, x_coverage, pixel_coverage_x);
+            columns++;
+            src_y++;
+            box -= pixel_coverage_y;
+        }
+
+        /* downsample any leftovers */
+        if (box > 0)
+        {
+	    scanline = orig + src_y * orig_stride / 4;
+            downsample_row_box_filter (start_column, width, scanline, temp_buf + width * columns, x_coverage, pixel_coverage_x);
+            columns++;
+        }
+
+        /* now scale the rows we just downsampled in the y direction */
+        downsample_columns_box_filter (width, start_coverage_y, pixel_coverage_y, temp_buf, dest);
+        dest += dst_stride / 4;
+
+//        assert(width*columns <= ((orig_height + scaled_height-1)/scaled_height+1) * width);
+    }
+//    assert (src_y<=orig_height);
+
+    retval = gTrue;
+
+cleanup:
+    free (x_coverage);
+    free (y_coverage);
+    free (temp_buf);
+
+    return gTrue;
+}
diff --git a/poppler/CairoRescaleBox.h b/poppler/CairoRescaleBox.h
new file mode 100644
index 0000000..5349c87
--- /dev/null
+++ b/poppler/CairoRescaleBox.h
@@ -0,0 +1,12 @@
+#ifndef CAIRO_RESCALE_BOX_H
+#define CAIRO_RESCALE_BOX_H
+
+#include "goo/gtypes.h"
+
+GBool downscale_box_filter(unsigned int *orig, int orig_stride, unsigned orig_width, unsigned orig_height,
+			   signed scaled_width, signed scaled_height,
+			   unsigned short int start_column, unsigned short int start_row,
+			   unsigned short int width, unsigned short int height,
+			   unsigned int *dest, int dst_stride);
+
+#endif /* CAIRO_RESCALE_BOX_H */
diff --git a/poppler/Makefile.am b/poppler/Makefile.am
index ec79e31..096ea76 100644
--- a/poppler/Makefile.am
+++ b/poppler/Makefile.am
@@ -47,7 +47,9 @@ libpoppler_cairo_la_SOURCES =			\
 	CairoFontEngine.cc			\
 	CairoFontEngine.h			\
 	CairoOutputDev.cc			\
-	CairoOutputDev.h
+	CairoOutputDev.h			\
+	CairoRescaleBox.cc			\
+	CairoRescaleBox.h
 
 endif