Firstly, I wrote a simple grid render operation, which just renders a grid of lines and is fairly similar (thought not identical) to the filter in gimp.
Secondly, I made a small change to the checkerboard operation to remove a couple of arbitrary constants, and to reverse the offset direction so that positive offsets shift the pattern to the right or downwards.
Please let me know if there are any issues, and I shall continue with some slightly more complex operations.
Andy.
From 2c94d37460262b19210296f68be53271797c13d6 Mon Sep 17 00:00:00 2001 From: Andy Gill <andyggill@xxxxxxxxx> Date: Thu, 13 Jan 2011 21:40:23 +0000 Subject: [PATCH 1/2] added simple grid render operation --- operations/common/grid.c | 130 ++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 130 insertions(+), 0 deletions(-) create mode 100644 operations/common/grid.c diff --git a/operations/common/grid.c b/operations/common/grid.c new file mode 100644 index 0000000..8fe89c2 --- /dev/null +++ b/operations/common/grid.c @@ -0,0 +1,130 @@ +/* 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 <http://www.gnu.org/licenses/>. + * + * Copyright 2006 Ãyvind KolÃs <pippin@xxxxxxxx> + */ + +#include "config.h" +#include <glib/gi18n-lib.h> + +#ifdef GEGL_CHANT_PROPERTIES + +gegl_chant_int (x, _("Width"), 1, G_MAXINT, 32, + _("Horizontal width of cells pixels.")) +gegl_chant_int (y, _("Height"), 1, G_MAXINT, 32, + _("Vertical width of cells in pixels.")) +gegl_chant_int (x_offset, _("X offset"), -G_MAXINT, G_MAXINT, 0, + _("Horizontal offset (from origin) for start of grid.")) +gegl_chant_int (y_offset, _("Y offset"), -G_MAXINT, G_MAXINT, 0, + _("Vertical offset (from origin) for start of grid.")) +gegl_chant_int (line_width, _("Line Width"), 0, G_MAXINT, 4, + _("Width of grid lines in pixels.")) +gegl_chant_int (line_height, _("Line Height"), 0, G_MAXINT, 4, + _("Height of grid lines in pixels.")) +gegl_chant_color (line_color, _("Color"), "black", + _("Color of the grid lines")) + +#else + +#define GEGL_CHANT_TYPE_POINT_RENDER +#define GEGL_CHANT_C_FILE "grid.c" + +#include "gegl-chant.h" + +static void +prepare (GeglOperation *operation) +{ + gegl_operation_set_format (operation, "output", babl_format ("RGBA float")); +} + +static GeglRectangle +get_bounding_box (GeglOperation *operation) +{ + return gegl_rectangle_infinite_plane (); +} + +static gboolean +process (GeglOperation *operation, + void *out_buf, + glong n_pixels, + const GeglRectangle *roi) +{ + GeglChantO *o = GEGL_CHANT_PROPERTIES (operation); + gfloat *out_pixel = out_buf; + gfloat line_color[4]; + gint x = roi->x; /* initial x */ + gint y = roi->y; /* and y coordinates */ + + gegl_color_get_rgba4f (o->line_color, line_color); + + while (n_pixels--) + { + gint nx,ny; + + nx = (x - o->x_offset) % o->x; + ny = (y - o->y_offset) % o->y; + /* handle case where % returns a negative number */ + nx += nx < 0 ? o->x : 0; + ny += ny < 0 ? o->y : 0; + + if (nx < o->line_width || ny < o->line_height) + { + out_pixel[0]=line_color[0]; + out_pixel[1]=line_color[1]; + out_pixel[2]=line_color[2]; + out_pixel[3]=line_color[3]; + } + else + { + out_pixel[0]=0.0f; + out_pixel[1]=0.0f; + out_pixel[2]=0.0f; + out_pixel[3]=0.0f; + } + + out_pixel += 4; + + /* update x and y coordinates */ + x++; + if (x>=roi->x + roi->width) + { + x=roi->x; + y++; + } + } + + return TRUE; +} + + +static void +gegl_chant_class_init (GeglChantClass *klass) +{ + GeglOperationClass *operation_class; + GeglOperationPointRenderClass *point_render_class; + + operation_class = GEGL_OPERATION_CLASS (klass); + point_render_class = GEGL_OPERATION_POINT_RENDER_CLASS (klass); + + point_render_class->process = process; + operation_class->get_bounding_box = get_bounding_box; + operation_class->prepare = prepare; + + operation_class->name = "gegl:grid"; + operation_class->categories = "render"; + operation_class->description = _("Grid renderer"); +} + +#endif -- 1.7.1
From c967576d165a8a36a948c22b848c415d50bf9150 Mon Sep 17 00:00:00 2001
From: Andy Gill <andyggill@xxxxxxxxx>
Date: Thu, 13 Jan 2011 21:47:47 +0000
Subject: [PATCH 2/2] removed arbitrary constants and reversed offset direction
---
operations/common/checkerboard.c | 10 ++++++----
1 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/operations/common/checkerboard.c b/operations/common/checkerboard.c
index fefc5fc..0896d0e 100644
--- a/operations/common/checkerboard.c
+++ b/operations/common/checkerboard.c
@@ -50,8 +50,7 @@ prepare (GeglOperation *operation)
static GeglRectangle
get_bounding_box (GeglOperation *operation)
{
- GeglRectangle result = {-10000000, -10000000, 20000000, 20000000};
- return result;
+ return gegl_rectangle_infinite_plane ();
}
static gboolean
@@ -74,8 +73,11 @@ process (GeglOperation *operation,
{
gint nx,ny;
- nx = ((x + o->x_offset + 100000 * o->x)/o->x) ;
- ny = ((y + o->y_offset + 100000 * o->y)/o->y) ;
+ nx = (x - o->x_offset)/o->x;
+ ny = (y - o->y_offset)/o->y;
+ /* shift negative cell indices, because / rounds towards zero. */
+ nx -= (x - o->x_offset) < 0 ? 1 : 0;
+ ny -= (y - o->y_offset) < 0 ? 1 : 0;
if ( (nx+ny) % 2 == 0)
{
--
1.7.1
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