| /* -*- 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. |
| */ |
| |
| //======================================================================== |
| // |
| // Modified under the Poppler project - http://poppler.freedesktop.org |
| // |
| // All changes made under the Poppler project to this file are licensed |
| // under GPL version 2 or later |
| // |
| // Copyright (C) 2012 Hib Eris <hib@hiberis.nl> |
| // |
| // To see a description of the changes please see the Changelog file that |
| // came with your tarball or type make ChangeLog if you are building from git |
| // |
| //======================================================================== |
| |
| /* 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 "goo/gtypes_p.h" |
| #include "CairoRescaleBox.h" |
| |
| |
| /* 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 retval; |
| } |
