one_texture.c

   1 /*
   2  * This program is free software; you can redistribute it and/or
   3  * modify it under the terms of the GNU General Public License
   4  * as published by the Free Software Foundation; either version 2
   5  * of the License, or (at your option) any later version.
   6  *
   7  * This program is distributed in the hope that it will be useful,
   8  * but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  * GNU General Public License for more details.
  11  *
  12  * You should have received a copy of the GNU General Public License
  13  * along with this program; if not, write to the Free Software
  14  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  15  *
  16  * See the COPYING file for license information.
  17  *
  18  * Guillaume Chazarain <booh@altern.org>
  19  */
  20
  21 /*****************************
  22  * Texture for small images. *
  23  *****************************/
  24
  25 #include <math.h>
  26 #include "gliv.h"
  27
  28 /* Draws the unique rectangle. */
  29 static void list_one(gliv_image * im)
  30 {
  31     GLfloat x0, y0;
  32     GLfloat xi, yi;
  33     GLfloat xmax, ymax;
  34
  35     im->list = glGenLists(1);
  36     glNewList(im->list, GL_COMPILE);
  37
  38     /* (x0;y0) : origin of the image. */
  39     x0 = -(im->width / 2);
  40     y0 = -(im->height / 2);
  41
  42     /* Size of the displayed image. */
  43     xi = im->width;
  44     yi = im->height;
  45
  46     /* Size of the interesting part of the texture. */
  47     xmax = (GLfloat) (im->width - .5) / im->gl_width;
  48     ymax = (GLfloat) (im->height - .5) / im->gl_height;
  49
  50     glBindTexture(GL_TEXTURE_2D, im->textures[0]);
  51
  52     /* Draw the rectangle. */
  53     glBegin(GL_QUADS);
  54
  55     glTexCoord2i(0, 0);
  56     glVertex2f(x0, y0);
  57
  58     glTexCoord2f(xmax, 0.0);
  59     glVertex2f(x0 + xi, y0);
  60
  61     glTexCoord2f(xmax, ymax);
  62     glVertex2f(x0 + xi, y0 + yi);
  63
  64     glTexCoord2f(0.0, ymax);
  65     glVertex2f(x0, y0 + yi);
  66
  67     glEnd();
  68     glEndList();
  69 }
  70
  71 /*
  72  * Returns the lowest power of two bigger than the argument.
  73  * We can't avoid linking with -lm so we use it.
  74  */
  75 static guint p2(guint p)
  76 {
  77     guint exponent;
  78
  79     exponent = ceil(log((float) p) / M_LN2);
  80
  81     return (guint) pow(2.0, (float) exponent);
  82 }
  83
  84 /* Creates one texture with powers of two as width and height. */
  85 void make_one_texture(gliv_image * im)
  86 {
  87     DATA32 *ptr;
  88
  89     im->gl_width = p2(im->width);
  90     im->gl_height = p2(im->height);
  91
  92     im->nb_width = im->nb_height = 1;
  93
  94     make_texture_image(im);
  95
  96     imlib_context_set_image(im->gl_im);
  97     ptr = imlib_image_get_data_for_reading_only();
  98
  99     glBindTexture(GL_TEXTURE_2D, im->textures[0]);
 100     texture_parameter();
 101     glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, im->gl_width, im->gl_height,
 102                  0, GL_RGBA, GL_UNSIGNED_BYTE, ptr);
 103
 104     list_one(im);
 105 }