NAME

       vpGetImage - get a field of the intermediate image

SYNOPSIS

       #include <volpack.h>

       vpResult
       vpGetImage(vpc, image, width, height, scan_bytes, pixel_type, image_type)
           vpContext *vpc;
           void *image;
           int width, height;
           int scan_bytes;
           int pixel_type, image_type;

ARGUMENTS

       vpc    VolPack context from vpCreateContext.

       image  2D array for storing result image.

       width  Width of array in pixels.

       height Height of array in pixels.

       scan_bytes
              Number of bytes per scanline in array.

       pixel_type
              Code indicating the format of each pixel in the array.

       image_type
              Code indicating the source of the image data (VP_IMAGE_BUFFER or VP_SHADOW_BUFFER).

DESCRIPTION

       This  is  a  debugging  function.   It is used to retrieve the contents of one of the temporary rendering
       buffers used during rendering, namely the intermediate image or the shadow buffer.  Rendering consists of
       two  stages:  the  volume  is resampled and composited into the intermediate image to produce a distorted
       volume rendering, and then the intermediate image is warped into the final image.  If shadows are enabled
       then  the  shadow  buffer  is  used  during  the  first  stage  to incrementally compute which voxels are
       illuminated by the light source.  This function returns images produced during the  first  stage,  before
       the final warp.

       This function may be called after a call to one of the rendering routines (see vpRenderRawVolume(3)).  If
       the image_type argument is VP_IMAGE_BUFFER then data will be copied from  the  intermediate  image.   The
       pixel_type  argument specifies what information to copy and the format for storing the data in the output
       array.  The possible values for pixel_type are the same as for the  pixel_type  argument  to  vpSetImage.
       For  instance,  use VP_LUMINANCE to extract the grayscale intensity (assuming the current shader produces
       grayscale pixels).

       If the image_type argument is VP_SHADOW_BUFFER then data will be copied from the shadow buffer.  The only
       valid option for pixel_type is VP_ALPHA, since no color information is stored in the shadow buffer.

       See  vpSetImage  for  details  on  the  pixel  formats, the layout of the output array, and the remaining
       arguments.

       To find the  required  size  for  the  result  array,  use  vpGeti  with  the  VP_INTERMEDIATE_WIDTH  and
       VP_INTERMEDIATE_HEIGHT   options   (when  image_type  is  VP_IMAGE_BUFFER)  or  the  VP_SHADOW_WIDTH  and
       VP_SHADOW_HEIGHT options (when image_type is VP_SHADOW_BUFFER).

ERRORS

       The normal return value is VP_OK.  The following error return values are possible:

       VPERROR_BAD_SIZE
              The destination array size is incorrect or there is no intermediate image.

       VPERROR_BAD_OPTION
              The field argument is invalid.

SEE ALSO

       VolPack(3), vpRenderRawVolume(3), vpGeti(3)