Re: [Cython] Mapping a really strange typedef in Cython

[Robert Bradshaw]

On Jun 29, 2008, at 4:16 AM, Johannes Wienke wrote:

Hi again,

I'm struggling to get a really strange typedef working in Cython. The
original C (preprocessor) code looks like this:

#define IW_CTAB_SIZE    256
typedef guchar (*iwColtab)[3];

extern iwColtab iw_def_col_tab;

/* Color formats of the data for prev_render...() */
#define IW_RGB                  ((iwColtab)0)

// some more formats

#define IW_BW                   ((iwColtab)7)
#define IW_GRAY                 IW_BW
#define IW_INDEX                (iw_def_col_tab)

#define IW_COLFORMAT_MAX        IW_BW   /* last 'special' definition */



This definition was originally used like this:

void prev_colConvert (iwColtab ctab, gint r, gint g, gint b,
                      gint *rd, gint *gd, gint *bd)
{
        if (ctab == IW_RGB) {
                *rd = r;
                *gd = g;
                *bd = b;
        } else if (ctab == IW_BGR) {
                *rd = b;
                *gd = g;
                *bd = r;
        } else if (ctab > IW_COLFORMAT_MAX && r>=0 && r < IW_CTAB_SIZE){
                *rd = ctab[r][0];
                *gd = ctab[r][1];
                *bd = ctab[r][2];
        }

}

I need to be able to do the same thing in cython with this definition.
My current approach was simply using a enum to emulate it:

cdef extern from "gui/Gimage.h":

    ctypedef enum iwColtab:
        IW_RGB
        # ...
        IW_GRAY
        IW_CTAB_SIZE
        IW_COLFORMAT_MAX


work:

Error converting Pyrex file to C:
------------------------------------------------------------
...
    elif ctab == IW_YUV:
        return Color(1.164 * (r - 16) + 1.596 * (b - 128),

128),
                     1.164 * (r - 16) + 2.018 * (g - 128))
    elif (ctab > IW_COLFORMAT_MAX and r >= 0 and r < IW_CTAB_SIZE):
        return Color(ctab[r][0], ctab[r][1], ctab[r][2])
                        ^
------------------------------------------------------------

image_utils.pyx:144:25: Attempting to index non-array type 'iwColtab'



Thanks for the help
Johannes

The purpose of this strange construct was that one can use normal color spaces without struggling, but one is also able to use a custom color table. The normal color modes work like this, but using the color table doesn't 1.164 * (r - 16) - 0.813 * (b - 128) - 0.391 * (g - I really have no idea how to solve this. Has anyone got a solution for this?

- Robert

I'm not sure--what is the definition of iwColtab? An enum won't work here because one can't index into it (in Cython or in C) so I think the only thing to do here is to have two separate types (the enum, and iwColtab) and do some casting.

PGP.sig
Description: This is a digitally signed message part

_______________________________________________
Cython-dev mailing list
Cython-dev@codespeak.net
http://codespeak.net/mailman/listinfo/cython-dev