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Diffstat (limited to 'libs/pixman-0.40.0/pixman/pixman-filter.c')
| -rw-r--r-- | libs/pixman-0.40.0/pixman/pixman-filter.c | 478 |
1 files changed, 478 insertions, 0 deletions
diff --git a/libs/pixman-0.40.0/pixman/pixman-filter.c b/libs/pixman-0.40.0/pixman/pixman-filter.c new file mode 100644 index 0000000..5f3b752 --- /dev/null +++ b/libs/pixman-0.40.0/pixman/pixman-filter.c @@ -0,0 +1,478 @@ +/* + * Copyright 2012, Red Hat, Inc. + * Copyright 2012, Soren Sandmann + * + * 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 (including the next + * paragraph) 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. + * + * Author: Soren Sandmann <soren.sandmann@gmail.com> + */ +#include <string.h> +#include <stdlib.h> +#include <stdio.h> +#include <math.h> +#include <assert.h> +#ifdef HAVE_CONFIG_H +#include <config.h> +#endif +#include "pixman-private.h" + +typedef double (* kernel_func_t) (double x); + +typedef struct +{ + pixman_kernel_t kernel; + kernel_func_t func; + double width; +} filter_info_t; + +static double +impulse_kernel (double x) +{ + return (x == 0.0)? 1.0 : 0.0; +} + +static double +box_kernel (double x) +{ + return 1; +} + +static double +linear_kernel (double x) +{ + return 1 - fabs (x); +} + +static double +gaussian_kernel (double x) +{ +#define SQRT2 (1.4142135623730950488016887242096980785696718753769480) +#define SIGMA (SQRT2 / 2.0) + + return exp (- x * x / (2 * SIGMA * SIGMA)) / (SIGMA * sqrt (2.0 * M_PI)); +} + +static double +sinc (double x) +{ + if (x == 0.0) + return 1.0; + else + return sin (M_PI * x) / (M_PI * x); +} + +static double +lanczos (double x, int n) +{ + return sinc (x) * sinc (x * (1.0 / n)); +} + +static double +lanczos2_kernel (double x) +{ + return lanczos (x, 2); +} + +static double +lanczos3_kernel (double x) +{ + return lanczos (x, 3); +} + +static double +nice_kernel (double x) +{ + return lanczos3_kernel (x * 0.75); +} + +static double +general_cubic (double x, double B, double C) +{ + double ax = fabs(x); + + if (ax < 1) + { + return (((12 - 9 * B - 6 * C) * ax + + (-18 + 12 * B + 6 * C)) * ax * ax + + (6 - 2 * B)) / 6; + } + else if (ax < 2) + { + return ((((-B - 6 * C) * ax + + (6 * B + 30 * C)) * ax + + (-12 * B - 48 * C)) * ax + + (8 * B + 24 * C)) / 6; + } + else + { + return 0; + } +} + +static double +cubic_kernel (double x) +{ + /* This is the Mitchell-Netravali filter. + * + * (0.0, 0.5) would give us the Catmull-Rom spline, + * but that one seems to be indistinguishable from Lanczos2. + */ + return general_cubic (x, 1/3.0, 1/3.0); +} + +static const filter_info_t filters[] = +{ + { PIXMAN_KERNEL_IMPULSE, impulse_kernel, 0.0 }, + { PIXMAN_KERNEL_BOX, box_kernel, 1.0 }, + { PIXMAN_KERNEL_LINEAR, linear_kernel, 2.0 }, + { PIXMAN_KERNEL_CUBIC, cubic_kernel, 4.0 }, + { PIXMAN_KERNEL_GAUSSIAN, gaussian_kernel, 5.0 }, + { PIXMAN_KERNEL_LANCZOS2, lanczos2_kernel, 4.0 }, + { PIXMAN_KERNEL_LANCZOS3, lanczos3_kernel, 6.0 }, + { PIXMAN_KERNEL_LANCZOS3_STRETCHED, nice_kernel, 8.0 }, +}; + +/* This function scales @kernel2 by @scale, then + * aligns @x1 in @kernel1 with @x2 in @kernel2 and + * and integrates the product of the kernels across @width. + * + * This function assumes that the intervals are within + * the kernels in question. E.g., the caller must not + * try to integrate a linear kernel ouside of [-1:1] + */ +static double +integral (pixman_kernel_t kernel1, double x1, + pixman_kernel_t kernel2, double scale, double x2, + double width) +{ + if (kernel1 == PIXMAN_KERNEL_BOX && kernel2 == PIXMAN_KERNEL_BOX) + { + return width; + } + /* The LINEAR filter is not differentiable at 0, so if the + * integration interval crosses zero, break it into two + * separate integrals. + */ + else if (kernel1 == PIXMAN_KERNEL_LINEAR && x1 < 0 && x1 + width > 0) + { + return + integral (kernel1, x1, kernel2, scale, x2, - x1) + + integral (kernel1, 0, kernel2, scale, x2 - x1, width + x1); + } + else if (kernel2 == PIXMAN_KERNEL_LINEAR && x2 < 0 && x2 + width > 0) + { + return + integral (kernel1, x1, kernel2, scale, x2, - x2) + + integral (kernel1, x1 - x2, kernel2, scale, 0, width + x2); + } + else if (kernel1 == PIXMAN_KERNEL_IMPULSE) + { + assert (width == 0.0); + return filters[kernel2].func (x2 * scale); + } + else if (kernel2 == PIXMAN_KERNEL_IMPULSE) + { + assert (width == 0.0); + return filters[kernel1].func (x1); + } + else + { + /* Integration via Simpson's rule + * See http://www.intmath.com/integration/6-simpsons-rule.php + * 12 segments (6 cubic approximations) seems to produce best + * result for lanczos3.linear, which was the combination that + * showed the most errors. This makes sense as the lanczos3 + * filter is 6 wide. + */ +#define N_SEGMENTS 12 +#define SAMPLE(a1, a2) \ + (filters[kernel1].func ((a1)) * filters[kernel2].func ((a2) * scale)) + + double s = 0.0; + double h = width / N_SEGMENTS; + int i; + + s = SAMPLE (x1, x2); + + for (i = 1; i < N_SEGMENTS; i += 2) + { + double a1 = x1 + h * i; + double a2 = x2 + h * i; + s += 4 * SAMPLE (a1, a2); + } + + for (i = 2; i < N_SEGMENTS; i += 2) + { + double a1 = x1 + h * i; + double a2 = x2 + h * i; + s += 2 * SAMPLE (a1, a2); + } + + s += SAMPLE (x1 + width, x2 + width); + + return h * s * (1.0 / 3.0); + } +} + +static void +create_1d_filter (int width, + pixman_kernel_t reconstruct, + pixman_kernel_t sample, + double scale, + int n_phases, + pixman_fixed_t *p) +{ + double step; + int i; + + step = 1.0 / n_phases; + + for (i = 0; i < n_phases; ++i) + { + double frac = step / 2.0 + i * step; + pixman_fixed_t new_total; + int x, x1, x2; + double total, e; + + /* Sample convolution of reconstruction and sampling + * filter. See rounding.txt regarding the rounding + * and sample positions. + */ + + x1 = ceil (frac - width / 2.0 - 0.5); + x2 = x1 + width; + + total = 0; + for (x = x1; x < x2; ++x) + { + double pos = x + 0.5 - frac; + double rlow = - filters[reconstruct].width / 2.0; + double rhigh = rlow + filters[reconstruct].width; + double slow = pos - scale * filters[sample].width / 2.0; + double shigh = slow + scale * filters[sample].width; + double c = 0.0; + double ilow, ihigh; + + if (rhigh >= slow && rlow <= shigh) + { + ilow = MAX (slow, rlow); + ihigh = MIN (shigh, rhigh); + + c = integral (reconstruct, ilow, + sample, 1.0 / scale, ilow - pos, + ihigh - ilow); + } + + *p = (pixman_fixed_t)floor (c * 65536.0 + 0.5); + total += *p; + p++; + } + + /* Normalize, with error diffusion */ + p -= width; + total = 65536.0 / total; + new_total = 0; + e = 0.0; + for (x = x1; x < x2; ++x) + { + double v = (*p) * total + e; + pixman_fixed_t t = floor (v + 0.5); + + e = v - t; + new_total += t; + *p++ = t; + } + + /* pixman_fixed_e's worth of error may remain; put it + * at the first sample, since that is the only one that + * hasn't had any error diffused into it. + */ + *(p - width) += pixman_fixed_1 - new_total; + } +} + + +static int +filter_width (pixman_kernel_t reconstruct, pixman_kernel_t sample, double size) +{ + return ceil (filters[reconstruct].width + size * filters[sample].width); +} + +#ifdef PIXMAN_GNUPLOT + +/* If enable-gnuplot is configured, then you can pipe the output of a + * pixman-using program to gnuplot and get a continuously-updated plot + * of the horizontal filter. This works well with demos/scale to test + * the filter generation. + * + * The plot is all the different subposition filters shuffled + * together. This is misleading in a few cases: + * + * IMPULSE.BOX - goes up and down as the subfilters have different + * numbers of non-zero samples + * IMPULSE.TRIANGLE - somewhat crooked for the same reason + * 1-wide filters - looks triangular, but a 1-wide box would be more + * accurate + */ +static void +gnuplot_filter (int width, int n_phases, const pixman_fixed_t* p) +{ + double step; + int i, j; + int first; + + step = 1.0 / n_phases; + + printf ("set style line 1 lc rgb '#0060ad' lt 1 lw 0.5 pt 7 pi 1 ps 0.5\n"); + printf ("plot [x=%g:%g] '-' with linespoints ls 1\n", -width*0.5, width*0.5); + /* Print a point at the origin so that y==0 line is included: */ + printf ("0 0\n\n"); + + /* The position of the first sample of the phase corresponding to + * frac is given by: + * + * ceil (frac - width / 2.0 - 0.5) + 0.5 - frac + * + * We have to find the frac that minimizes this expression. + * + * For odd widths, we have + * + * ceil (frac - width / 2.0 - 0.5) + 0.5 - frac + * = ceil (frac) + K - frac + * = 1 + K - frac + * + * for some K, so this is minimized when frac is maximized and + * strictly growing with frac. So for odd widths, we can simply + * start at the last phase and go backwards. + * + * For even widths, we have + * + * ceil (frac - width / 2.0 - 0.5) + 0.5 - frac + * = ceil (frac - 0.5) + K - frac + * + * The graph for this function (ignoring K) looks like this: + * + * 0.5 + * | |\ + * | | \ + * | | \ + * 0 | | \ + * |\ | + * | \ | + * | \ | + * -0.5 | \| + * --------------------------------- + * 0 0.5 1 + * + * So in this case we need to start with the phase whose frac is + * less than, but as close as possible to 0.5, then go backwards + * until we hit the first phase, then wrap around to the last + * phase and continue backwards. + * + * Which phase is as close as possible 0.5? The locations of the + * sampling point corresponding to the kth phase is given by + * 1/(2 * n_phases) + k / n_phases: + * + * 1/(2 * n_phases) + k / n_phases = 0.5 + * + * from which it follows that + * + * k = (n_phases - 1) / 2 + * + * rounded down is the phase in question. + */ + if (width & 1) + first = n_phases - 1; + else + first = (n_phases - 1) / 2; + + for (j = 0; j < width; ++j) + { + for (i = 0; i < n_phases; ++i) + { + int phase = first - i; + double frac, pos; + + if (phase < 0) + phase = n_phases + phase; + + frac = step / 2.0 + phase * step; + pos = ceil (frac - width / 2.0 - 0.5) + 0.5 - frac + j; + + printf ("%g %g\n", + pos, + pixman_fixed_to_double (*(p + phase * width + j))); + } + } + + printf ("e\n"); + fflush (stdout); +} + +#endif + +/* Create the parameter list for a SEPARABLE_CONVOLUTION filter + * with the given kernels and scale parameters + */ +PIXMAN_EXPORT pixman_fixed_t * +pixman_filter_create_separable_convolution (int *n_values, + pixman_fixed_t scale_x, + pixman_fixed_t scale_y, + pixman_kernel_t reconstruct_x, + pixman_kernel_t reconstruct_y, + pixman_kernel_t sample_x, + pixman_kernel_t sample_y, + int subsample_bits_x, + int subsample_bits_y) +{ + double sx = fabs (pixman_fixed_to_double (scale_x)); + double sy = fabs (pixman_fixed_to_double (scale_y)); + pixman_fixed_t *params; + int subsample_x, subsample_y; + int width, height; + + width = filter_width (reconstruct_x, sample_x, sx); + subsample_x = (1 << subsample_bits_x); + + height = filter_width (reconstruct_y, sample_y, sy); + subsample_y = (1 << subsample_bits_y); + + *n_values = 4 + width * subsample_x + height * subsample_y; + + params = malloc (*n_values * sizeof (pixman_fixed_t)); + if (!params) + return NULL; + + params[0] = pixman_int_to_fixed (width); + params[1] = pixman_int_to_fixed (height); + params[2] = pixman_int_to_fixed (subsample_bits_x); + params[3] = pixman_int_to_fixed (subsample_bits_y); + + create_1d_filter (width, reconstruct_x, sample_x, sx, subsample_x, + params + 4); + create_1d_filter (height, reconstruct_y, sample_y, sy, subsample_y, + params + 4 + width * subsample_x); + +#ifdef PIXMAN_GNUPLOT + gnuplot_filter(width, subsample_x, params + 4); +#endif + + return params; +} |