GEGL Operation API
brightness-contrast.c
/* This file is an image processing operation for GEGL
*
* GEGL is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 3 of the License, or (at your option) any later version.
*
* GEGL 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with GEGL; if not, see <https://www.gnu.org/licenses/>.
*
* Copyright 2006 Øyvind Kolås <pippin@gimp.org>
*/
#include "config.h"
#include <glib/gi18n-lib.h>
#ifdef GEGL_PROPERTIES
/* Here in the top of the file the properties of the operation is declared,
* this causes the declaration of a structure for containing the data.
*
* The first member of each property_ macro becomes a struct member
* in the GeglProperties struct used when processing.
*/
property_double (contrast, _("Contrast"), 1.0)
description (_("Magnitude of contrast scaling >1.0 brighten < 1.0 darken"))
value_range (-5.0, 5.0)
ui_range (0.0, 2.0)
property_double (brightness, _("Brightness"), 0.0)
description (_("Amount to increase brightness"))
value_range (-3.0, 3.0)
ui_range (-1.0, 1.0)
#else
/* Specify the base class we're building our operation on, the base
* class provides a lot of the legwork so we do not have to. For
* brightness contrast the best base class is the POINT_FILTER base
* class.
*/
#define GEGL_OP_POINT_FILTER
/* The C prefix used for some generated functions
*/
#define GEGL_OP_NAME brightness_contrast
/* We specify the file we're in, this is needed to make the code
* generation for the properties work.
*/
#define GEGL_OP_C_SOURCE brightness-contrast.c
/* Including gegl-op.h creates most of the GObject boiler plate
* needed, creating a GeglOp instance structure a GeglOpClass
* structure for our operation, as well as the needed code to register
* our new gobject with GEGL.
*/
#include "gegl-op.h"
/* prepare() is called on each operation providing data to a node that
* is requested to provide a rendered result. When prepare is called
* all properties are known. For brightness contrast we use this
* opportunity to dictate the formats of the input and output buffers.
*
* since we want to work on linear data, as indicated with "RGBA float" we
* strictly speaking wouldn't need to have a prepare() since the default
* implementation does the same.
*/
static void prepare (GeglOperation *operation)
{
const Babl *space = gegl_operation_get_source_space (operation, "input");
gegl_operation_set_format (operation, "input", babl_format_with_space ("RGBA float", space));
gegl_operation_set_format (operation, "output", babl_format_with_space ("RGBA float", space));
}
/* For GeglOperationPointFilter subclasses, we operate on linear
* buffers with a pixel count.
*/
static gboolean
process (GeglOperation *op,
void *in_buf,
void *out_buf,
glong n_pixels,
const GeglRectangle *roi,
gint level)
{
/* Retrieve a pointer to GeglProperties structure which contains all the
* chanted properties
*/
GeglProperties *o = GEGL_PROPERTIES (op);
gfloat * GEGL_ALIGNED in_pixel;
gfloat * GEGL_ALIGNED out_pixel;
gfloat brightness, contrast;
glong i;
in_pixel = in_buf;
out_pixel = out_buf;
brightness = o->brightness;
contrast = o->contrast;
for (i=0; i<n_pixels; i++)
{
out_pixel[0] = (in_pixel[0] - 0.5f) * contrast + brightness + 0.5;
out_pixel[1] = (in_pixel[1] - 0.5f) * contrast + brightness + 0.5;
out_pixel[2] = (in_pixel[2] - 0.5f) * contrast + brightness + 0.5;
out_pixel[3] = in_pixel[3]; /* copy the alpha */
in_pixel += 4;
out_pixel += 4;
}
return TRUE;
}
#include "opencl/brightness-contrast.cl.h"
/*
* The class init function sets up information needed for this operations class
* (template) in the GObject OO framework.
*/
static void
gegl_op_class_init (GeglOpClass *klass)
{
GeglOperationClass *operation_class;
GeglOperationPointFilterClass *point_filter_class;
gchar *composition =
"<?xml version='1.0' encoding='UTF-8'?>"
"<gegl>"
" <node operation='gegl:crop' width='200' height='200'/>"
" <node operation='gegl:over'>"
" <node operation='gegl:brightness-contrast'>"
" <params>"
" <param name='contrast'>1.8</param>"
" <param name='brightness'>0.25</param>"
" </params>"
" </node>"
" <node operation='gegl:load' path='standard-input.png'/>"
" </node>"
" <node operation='gegl:checkerboard'>"
" <params>"
" <param name='color1'>rgb(0.25,0.25,0.25)</param>"
" <param name='color2'>rgb(0.75,0.75,0.75)</param>"
" </params>"
" </node>"
"</gegl>";
operation_class = GEGL_OPERATION_CLASS (klass);
point_filter_class = GEGL_OPERATION_POINT_FILTER_CLASS (klass);
/* override the prepare methods of the GeglOperation class */
operation_class->prepare = prepare;
/* override the process method of the point filter class (the process methods
* of our superclasses deal with the handling on their level of abstraction)
*/
point_filter_class->process = process;
gegl_operation_class_set_keys (operation_class,
"name", "gegl:brightness-contrast",
"title", _("Brightness Contrast"),
"categories", "color",
"reference-hash", "d71a0399eb2edc30e86d7ee54e5d5d56",
/* xgettext:no-c-format */
"description", _("Changes the light level and contrast. This operation operates in linear light, 'contrast' is a scale factor around 50% gray, and 'brightness' a constant offset to apply after contrast scaling."),
"cl-source" , brightness_contrast_cl_source,
"reference-composition", composition,
NULL);
}
#endif /* closing #ifdef GEGL_PROPERTIES ... else ... */