gecko-dev/other-licenses/libart_lgpl/art_render_gradient.c

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C

/*
* art_render_gradient.c: Gradient image source for modular rendering.
*
* Libart_LGPL - library of basic graphic primitives
* Copyright (C) 2000 Raph Levien
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*
* Authors: Raph Levien <raph@acm.org>
* Alexander Larsson <alla@lysator.liu.se>
*/
#include <math.h>
#include "art_misc.h"
#include "art_alphagamma.h"
#include "art_filterlevel.h"
#include "art_render.h"
#include "art_render_gradient.h"
typedef struct _ArtImageSourceGradLin ArtImageSourceGradLin;
typedef struct _ArtImageSourceGradRad ArtImageSourceGradRad;
struct _ArtImageSourceGradLin {
ArtImageSource super;
const ArtGradientLinear *gradient;
};
struct _ArtImageSourceGradRad {
ArtImageSource super;
const ArtGradientRadial *gradient;
double a;
};
#define EPSILON 1e-6
/**
* art_render_gradient_setpix: Set a gradient pixel.
* @render: The render object.
* @dst: Pointer to destination (where to store pixel).
* @n_stops: Number of stops in @stops.
* @stops: The stops for the gradient.
* @offset: The offset.
*
* @n_stops must be > 0.
*
* Sets a gradient pixel, storing it at @dst.
**/
static void
art_render_gradient_setpix (ArtRender *render,
art_u8 *dst,
int n_stops, ArtGradientStop *stops,
double offset)
{
int ix;
int j;
double off0, off1;
int n_ch = render->n_chan + 1;
for (ix = 0; ix < n_stops; ix++)
if (stops[ix].offset > offset)
break;
/* stops[ix - 1].offset < offset < stops[ix].offset */
if (ix > 0 && ix < n_stops)
{
off0 = stops[ix - 1].offset;
off1 = stops[ix].offset;
if (fabs (off1 - off0) > EPSILON)
{
double interp;
interp = (offset - off0) / (off1 - off0);
for (j = 0; j < n_ch; j++)
{
int z0, z1;
int z;
z0 = stops[ix - 1].color[j];
z1 = stops[ix].color[j];
z = floor (z0 + (z1 - z0) * interp + 0.5);
if (render->buf_depth == 8)
dst[j] = ART_PIX_8_FROM_MAX (z);
else /* (render->buf_depth == 16) */
((art_u16 *)dst)[j] = z;
}
return;
}
}
else if (ix == n_stops)
ix--;
for (j = 0; j < n_ch; j++)
{
int z;
z = stops[ix].color[j];
if (render->buf_depth == 8)
dst[j] = ART_PIX_8_FROM_MAX (z);
else /* (render->buf_depth == 16) */
((art_u16 *)dst)[j] = z;
}
}
static void
art_render_gradient_linear_done (ArtRenderCallback *self, ArtRender *render)
{
art_free (self);
}
static void
art_render_gradient_linear_render (ArtRenderCallback *self, ArtRender *render,
art_u8 *dest, int y)
{
ArtImageSourceGradLin *z = (ArtImageSourceGradLin *)self;
const ArtGradientLinear *gradient = z->gradient;
int pixstride = (render->n_chan + 1) * (render->depth >> 3);
int x;
int width = render->x1 - render->x0;
double offset, d_offset;
double actual_offset;
int n_stops = gradient->n_stops;
ArtGradientStop *stops = gradient->stops;
art_u8 *bufp = render->image_buf;
ArtGradientSpread spread = gradient->spread;
offset = render->x0 * gradient->a + y * gradient->b + gradient->c;
d_offset = gradient->a;
for (x = 0; x < width; x++)
{
if (spread == ART_GRADIENT_PAD)
actual_offset = offset;
else if (spread == ART_GRADIENT_REPEAT)
actual_offset = offset - floor (offset);
else /* (spread == ART_GRADIENT_REFLECT) */
{
double tmp;
tmp = offset - 2 * floor (0.5 * offset);
actual_offset = tmp > 1 ? 2 - tmp : tmp;
}
art_render_gradient_setpix (render, bufp, n_stops, stops, actual_offset);
offset += d_offset;
bufp += pixstride;
}
}
static void
art_render_gradient_linear_negotiate (ArtImageSource *self, ArtRender *render,
ArtImageSourceFlags *p_flags,
int *p_buf_depth, ArtAlphaType *p_alpha)
{
self->super.render = art_render_gradient_linear_render;
*p_flags = 0;
*p_buf_depth = render->depth;
*p_alpha = ART_ALPHA_PREMUL;
}
/**
* art_render_gradient_linear: Add a linear gradient image source.
* @render: The render object.
* @gradient: The linear gradient.
*
* Adds the linear gradient @gradient as the image source for rendering
* in the render object @render.
**/
void
art_render_gradient_linear (ArtRender *render,
const ArtGradientLinear *gradient,
ArtFilterLevel level)
{
ArtImageSourceGradLin *image_source = art_new (ArtImageSourceGradLin, 1);
image_source->super.super.render = NULL;
image_source->super.super.done = art_render_gradient_linear_done;
image_source->super.negotiate = art_render_gradient_linear_negotiate;
image_source->gradient = gradient;
art_render_add_image_source (render, &image_source->super);
}
static void
art_render_gradient_radial_done (ArtRenderCallback *self, ArtRender *render)
{
art_free (self);
}
static void
art_render_gradient_radial_render (ArtRenderCallback *self, ArtRender *render,
art_u8 *dest, int y)
{
ArtImageSourceGradRad *z = (ArtImageSourceGradRad *)self;
const ArtGradientRadial *gradient = z->gradient;
int pixstride = (render->n_chan + 1) * (render->depth >> 3);
int x;
int x0 = render->x0;
int width = render->x1 - x0;
int n_stops = gradient->n_stops;
ArtGradientStop *stops = gradient->stops;
art_u8 *bufp = render->image_buf;
double fx = gradient->fx;
double fy = gradient->fy;
double dx, dy;
const double *affine = gradient->affine;
double aff0 = affine[0];
double aff1 = affine[1];
const double a = z->a;
const double arecip = 1.0 / a;
double b, db;
double c, dc, ddc;
double b_a, db_a;
double rad, drad, ddrad;
dx = x0 * aff0 + y * affine[2] + affine[4] - fx;
dy = x0 * aff1 + y * affine[3] + affine[5] - fy;
b = dx * fx + dy * fy;
db = aff0 * fx + aff1 * fy;
c = dx * dx + dy * dy;
dc = 2 * aff0 * dx + aff0 * aff0 + 2 * aff1 * dy + aff1 * aff1;
ddc = 2 * aff0 * aff0 + 2 * aff1 * aff1;
b_a = b * arecip;
db_a = db * arecip;
rad = b_a * b_a + c * arecip;
drad = 2 * b_a * db_a + db_a * db_a + dc * arecip;
ddrad = 2 * db_a * db_a + ddc * arecip;
for (x = 0; x < width; x++)
{
double z;
if (rad > 0)
z = b_a + sqrt (rad);
else
z = b_a;
art_render_gradient_setpix (render, bufp, n_stops, stops, z);
bufp += pixstride;
b_a += db_a;
rad += drad;
drad += ddrad;
}
}
static void
art_render_gradient_radial_negotiate (ArtImageSource *self, ArtRender *render,
ArtImageSourceFlags *p_flags,
int *p_buf_depth, ArtAlphaType *p_alpha)
{
self->super.render = art_render_gradient_radial_render;
*p_flags = 0;
*p_buf_depth = render->depth;
*p_alpha = ART_ALPHA_PREMUL;
}
/**
* art_render_gradient_radial: Add a radial gradient image source.
* @render: The render object.
* @gradient: The radial gradient.
*
* Adds the radial gradient @gradient as the image source for rendering
* in the render object @render.
**/
void
art_render_gradient_radial (ArtRender *render,
const ArtGradientRadial *gradient,
ArtFilterLevel level)
{
ArtImageSourceGradRad *image_source = art_new (ArtImageSourceGradRad, 1);
double fx = gradient->fx;
double fy = gradient->fy;
image_source->super.super.render = NULL;
image_source->super.super.done = art_render_gradient_radial_done;
image_source->super.negotiate = art_render_gradient_radial_negotiate;
image_source->gradient = gradient;
/* todo: sanitycheck fx, fy? */
image_source->a = 1 - fx * fx - fy * fy;
art_render_add_image_source (render, &image_source->super);
}