Converting a pixel to a given format/type (original) (raw)

Next: Binary images Up: Image file I/O Previous: Filling an image with Contents Gandalf routines taking Gan_Pixel structure pointers as arguments, such as gan_image_fill_const(), require that the format and type of the pixel and image arguments match. This can be done by using the routines in this section. To convert a pixel to a specific format and type use the routine

  Gan_Pixel Pixel1, Pixel2; /* declare pixels 1 & 2 */

  /* let's initialise pixel 1 to a grey-level unsigned character value */
  Pixel1.format = GAN_GREY_LEVEL_IMAGE;
  Pixel1.type = GAN_UCHAR;
  Pixel1.data.gl.uc = 255;

  /* now convert pixel to RGB format and floating point type */
  gan_image_convert_pixel_q ( &Pixel1, GAN_RGB_COLOUR_IMAGE, GAN_FLOAT,
                              &Pixel2 );

  /* print new pixel value, which should be R=G=B=1 */
  printf ( "pixel RGB value %f %f %f\n", Pixel2.data.rgb.f.R,
           Pixel2.data.rgb.f.G, Pixel2.data.rgb.f.B );

Another version of this function returns the result as a new pixel:

  /* convert pixel to RGB format and floating point type */
  Pixel2 = gan_image_convert_pixel_s ( &Pixel1, GAN_RGB_COLOUR_IMAGE, GAN_FLOAT );

There is also a routine that converts the format and type in-place in the input pixel:

  /* convert pixel to RGB format and floating point type in-place */
  gan_image_convert_pixel_i ( &Pixel1, GAN_RGB_COLOUR_IMAGE, GAN_FLOAT );

2006-03-17