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cpython/Modules/imageop.c
Sjoerd Mullender 7e6bbe1516 The format of the string data used in the imageop module is described 
as "This is the same format as used by gl.lrectwrite() and the imgfile
module."  This implies a certain byte order in multi-byte pixel
formats.  However, the code was originally written on an SGI
(big-endian) and *uses* the fact that bytes are stored in a particular
order in ints.  This means that the code uses and produces different
byte order on little-endian systems.

This fix adds a module-level flag "backward_compatible" (default not
set, and if not set, behaves as if set to 1--i.e. backward compatible)
that can be used on a little-endian system to use the same byte order
as the SGI.  Using this flag it is then possible to prepare
SGI-compatible images on a little-endian system.

This patch is the result of a (small) discussion on python-dev and was
submitted to SourceForge as patch #874358.
2004-01-10 20:43:43 +00:00

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/* imageopmodule - Various operations on pictures */
#ifdef sun
#define signed
#endif
#include "Python.h"
#if SIZEOF_INT == 4
typedef int Py_Int32;
typedef unsigned int Py_UInt32;
#else
#if SIZEOF_LONG == 4
typedef long Py_Int32;
typedef unsigned long Py_UInt32;
#else
#error "No 4-byte integral type"
#endif
#endif
#define CHARP(cp, xmax, x, y) ((char *)(cp+y*xmax+x))
#define SHORTP(cp, xmax, x, y) ((short *)(cp+2*(y*xmax+x)))
#define LONGP(cp, xmax, x, y) ((Py_Int32 *)(cp+4*(y*xmax+x)))
static PyObject *ImageopError;
static PyObject *ImageopDict;
/* If this function returns true (the default if anything goes wrong), we're
behaving in a backward-compatible way with respect to how multi-byte pixels
are stored in the strings. The code in this module was originally written
for an SGI which is a big-endian system, and so the old code assumed that
4-byte integers hold the R, G, and B values in a particular order.
However, on little-endian systems the order is reversed, and so not
actually compatible with what gl.lrectwrite and imgfile expect.
(gl.lrectwrite and imgfile are also SGI-specific, however, it is
conceivable that the data handled here comes from or goes to an SGI or that
it is otherwise used in the expectation that the byte order in the strings
is as specified.)
The function returns the value of the module variable
"backward_compatible", or 1 if the variable does not exist or is not an
int.
*/
static int
imageop_backward_compatible(void)
{
static PyObject *bcos;
PyObject *bco;
long rc;
if (ImageopDict == NULL) /* "cannot happen" */
return 1;
if (bcos == NULL) {
/* cache string object for future use */
bcos = PyString_FromString("backward_compatible");
if (bcos == NULL)
return 1;
}
bco = PyDict_GetItem(ImageopDict, bcos);
if (bco == NULL)
return 1;
if (!PyInt_Check(bco))
return 1;
rc = PyInt_AsLong(bco);
if (PyErr_Occurred()) {
/* not an integer, or too large, or something */
PyErr_Clear();
rc = 1;
}
return rc != 0; /* convert to values 0, 1 */
}
static PyObject *
imageop_crop(PyObject *self, PyObject *args)
{
char *cp, *ncp;
short *nsp;
Py_Int32 *nlp;
int len, size, x, y, newx1, newx2, newy1, newy2;
int ix, iy, xstep, ystep;
PyObject *rv;
if ( !PyArg_ParseTuple(args, "s#iiiiiii", &cp, &len, &size, &x, &y,
&newx1, &newy1, &newx2, &newy2) )
return 0;
if ( size != 1 && size != 2 && size != 4 ) {
PyErr_SetString(ImageopError, "Size should be 1, 2 or 4");
return 0;
}
if ( len != size*x*y ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
xstep = (newx1 < newx2)? 1 : -1;
ystep = (newy1 < newy2)? 1 : -1;
rv = PyString_FromStringAndSize(NULL,
(abs(newx2-newx1)+1)*(abs(newy2-newy1)+1)*size);
if ( rv == 0 )
return 0;
ncp = (char *)PyString_AsString(rv);
nsp = (short *)ncp;
nlp = (Py_Int32 *)ncp;
newy2 += ystep;
newx2 += xstep;
for( iy = newy1; iy != newy2; iy+=ystep ) {
for ( ix = newx1; ix != newx2; ix+=xstep ) {
if ( iy < 0 || iy >= y || ix < 0 || ix >= x ) {
if ( size == 1 )
*ncp++ = 0;
else
*nlp++ = 0;
} else {
if ( size == 1 )
*ncp++ = *CHARP(cp, x, ix, iy);
else if ( size == 2 )
*nsp++ = *SHORTP(cp, x, ix, iy);
else
*nlp++ = *LONGP(cp, x, ix, iy);
}
}
}
return rv;
}
static PyObject *
imageop_scale(PyObject *self, PyObject *args)
{
char *cp, *ncp;
short *nsp;
Py_Int32 *nlp;
int len, size, x, y, newx, newy;
int ix, iy;
int oix, oiy;
PyObject *rv;
if ( !PyArg_ParseTuple(args, "s#iiiii",
&cp, &len, &size, &x, &y, &newx, &newy) )
return 0;
if ( size != 1 && size != 2 && size != 4 ) {
PyErr_SetString(ImageopError, "Size should be 1, 2 or 4");
return 0;
}
if ( len != size*x*y ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, newx*newy*size);
if ( rv == 0 )
return 0;
ncp = (char *)PyString_AsString(rv);
nsp = (short *)ncp;
nlp = (Py_Int32 *)ncp;
for( iy = 0; iy < newy; iy++ ) {
for ( ix = 0; ix < newx; ix++ ) {
oix = ix * x / newx;
oiy = iy * y / newy;
if ( size == 1 )
*ncp++ = *CHARP(cp, x, oix, oiy);
else if ( size == 2 )
*nsp++ = *SHORTP(cp, x, oix, oiy);
else
*nlp++ = *LONGP(cp, x, oix, oiy);
}
}
return rv;
}
/* Note: this routine can use a bit of optimizing */
static PyObject *
imageop_tovideo(PyObject *self, PyObject *args)
{
int maxx, maxy, x, y, len;
int i;
unsigned char *cp, *ncp;
int width;
PyObject *rv;
if ( !PyArg_ParseTuple(args, "s#iii", &cp, &len, &width, &maxx, &maxy) )
return 0;
if ( width != 1 && width != 4 ) {
PyErr_SetString(ImageopError, "Size should be 1 or 4");
return 0;
}
if ( maxx*maxy*width != len ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, len);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_AsString(rv);
if ( width == 1 ) {
memcpy(ncp, cp, maxx); /* Copy first line */
ncp += maxx;
for (y=1; y<maxy; y++) { /* Interpolate other lines */
for(x=0; x<maxx; x++) {
i = y*maxx + x;
*ncp++ = ((int)cp[i] + (int)cp[i-maxx]) >> 1;
}
}
} else {
memcpy(ncp, cp, maxx*4); /* Copy first line */
ncp += maxx*4;
for (y=1; y<maxy; y++) { /* Interpolate other lines */
for(x=0; x<maxx; x++) {
i = (y*maxx + x)*4 + 1;
*ncp++ = 0; /* Skip alfa comp */
*ncp++ = ((int)cp[i] + (int)cp[i-4*maxx]) >> 1;
i++;
*ncp++ = ((int)cp[i] + (int)cp[i-4*maxx]) >> 1;
i++;
*ncp++ = ((int)cp[i] + (int)cp[i-4*maxx]) >> 1;
}
}
}
return rv;
}
static PyObject *
imageop_grey2mono(PyObject *self, PyObject *args)
{
int tres, x, y, len;
unsigned char *cp, *ncp;
unsigned char ovalue;
PyObject *rv;
int i, bit;
if ( !PyArg_ParseTuple(args, "s#iii", &cp, &len, &x, &y, &tres) )
return 0;
if ( x*y != len ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, (len+7)/8);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_AsString(rv);
bit = 0x80;
ovalue = 0;
for ( i=0; i < len; i++ ) {
if ( (int)cp[i] > tres )
ovalue |= bit;
bit >>= 1;
if ( bit == 0 ) {
*ncp++ = ovalue;
bit = 0x80;
ovalue = 0;
}
}
if ( bit != 0x80 )
*ncp++ = ovalue;
return rv;
}
static PyObject *
imageop_grey2grey4(PyObject *self, PyObject *args)
{
int x, y, len;
unsigned char *cp, *ncp;
unsigned char ovalue;
PyObject *rv;
int i;
int pos;
if ( !PyArg_ParseTuple(args, "s#ii", &cp, &len, &x, &y) )
return 0;
if ( x*y != len ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, (len+1)/2);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_AsString(rv);
pos = 0;
ovalue = 0;
for ( i=0; i < len; i++ ) {
ovalue |= ((int)cp[i] & 0xf0) >> pos;
pos += 4;
if ( pos == 8 ) {
*ncp++ = ovalue;
ovalue = 0;
pos = 0;
}
}
if ( pos != 0 )
*ncp++ = ovalue;
return rv;
}
static PyObject *
imageop_grey2grey2(PyObject *self, PyObject *args)
{
int x, y, len;
unsigned char *cp, *ncp;
unsigned char ovalue;
PyObject *rv;
int i;
int pos;
if ( !PyArg_ParseTuple(args, "s#ii", &cp, &len, &x, &y) )
return 0;
if ( x*y != len ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, (len+3)/4);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_AsString(rv);
pos = 0;
ovalue = 0;
for ( i=0; i < len; i++ ) {
ovalue |= ((int)cp[i] & 0xc0) >> pos;
pos += 2;
if ( pos == 8 ) {
*ncp++ = ovalue;
ovalue = 0;
pos = 0;
}
}
if ( pos != 0 )
*ncp++ = ovalue;
return rv;
}
static PyObject *
imageop_dither2mono(PyObject *self, PyObject *args)
{
int sum, x, y, len;
unsigned char *cp, *ncp;
unsigned char ovalue;
PyObject *rv;
int i, bit;
if ( !PyArg_ParseTuple(args, "s#ii", &cp, &len, &x, &y) )
return 0;
if ( x*y != len ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, (len+7)/8);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_AsString(rv);
bit = 0x80;
ovalue = 0;
sum = 0;
for ( i=0; i < len; i++ ) {
sum += cp[i];
if ( sum >= 256 ) {
sum -= 256;
ovalue |= bit;
}
bit >>= 1;
if ( bit == 0 ) {
*ncp++ = ovalue;
bit = 0x80;
ovalue = 0;
}
}
if ( bit != 0x80 )
*ncp++ = ovalue;
return rv;
}
static PyObject *
imageop_dither2grey2(PyObject *self, PyObject *args)
{
int x, y, len;
unsigned char *cp, *ncp;
unsigned char ovalue;
PyObject *rv;
int i;
int pos;
int sum = 0, nvalue;
if ( !PyArg_ParseTuple(args, "s#ii", &cp, &len, &x, &y) )
return 0;
if ( x*y != len ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, (len+3)/4);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_AsString(rv);
pos = 1;
ovalue = 0;
for ( i=0; i < len; i++ ) {
sum += cp[i];
nvalue = sum & 0x180;
sum -= nvalue;
ovalue |= nvalue >> pos;
pos += 2;
if ( pos == 9 ) {
*ncp++ = ovalue;
ovalue = 0;
pos = 1;
}
}
if ( pos != 0 )
*ncp++ = ovalue;
return rv;
}
static PyObject *
imageop_mono2grey(PyObject *self, PyObject *args)
{
int v0, v1, x, y, len, nlen;
unsigned char *cp, *ncp;
PyObject *rv;
int i, bit;
if ( !PyArg_ParseTuple(args, "s#iiii", &cp, &len, &x, &y, &v0, &v1) )
return 0;
nlen = x*y;
if ( (nlen+7)/8 != len ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, nlen);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_AsString(rv);
bit = 0x80;
for ( i=0; i < nlen; i++ ) {
if ( *cp & bit )
*ncp++ = v1;
else
*ncp++ = v0;
bit >>= 1;
if ( bit == 0 ) {
bit = 0x80;
cp++;
}
}
return rv;
}
static PyObject *
imageop_grey22grey(PyObject *self, PyObject *args)
{
int x, y, len, nlen;
unsigned char *cp, *ncp;
PyObject *rv;
int i, pos, value = 0, nvalue;
if ( !PyArg_ParseTuple(args, "s#ii", &cp, &len, &x, &y) )
return 0;
nlen = x*y;
if ( (nlen+3)/4 != len ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, nlen);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_AsString(rv);
pos = 0;
for ( i=0; i < nlen; i++ ) {
if ( pos == 0 ) {
value = *cp++;
pos = 8;
}
pos -= 2;
nvalue = (value >> pos) & 0x03;
*ncp++ = nvalue | (nvalue << 2) |
(nvalue << 4) | (nvalue << 6);
}
return rv;
}
static PyObject *
imageop_grey42grey(PyObject *self, PyObject *args)
{
int x, y, len, nlen;
unsigned char *cp, *ncp;
PyObject *rv;
int i, pos, value = 0, nvalue;
if ( !PyArg_ParseTuple(args, "s#ii", &cp, &len, &x, &y) )
return 0;
nlen = x*y;
if ( (nlen+1)/2 != len ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, nlen);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_AsString(rv);
pos = 0;
for ( i=0; i < nlen; i++ ) {
if ( pos == 0 ) {
value = *cp++;
pos = 8;
}
pos -= 4;
nvalue = (value >> pos) & 0x0f;
*ncp++ = nvalue | (nvalue << 4);
}
return rv;
}
static PyObject *
imageop_rgb2rgb8(PyObject *self, PyObject *args)
{
int x, y, len, nlen;
unsigned char *cp;
unsigned char *ncp;
PyObject *rv;
int i, r, g, b;
int backward_compatible = imageop_backward_compatible();
if ( !PyArg_ParseTuple(args, "s#ii", &cp, &len, &x, &y) )
return 0;
nlen = x*y;
if ( nlen*4 != len ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, nlen);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_AsString(rv);
for ( i=0; i < nlen; i++ ) {
/* Bits in source: aaaaaaaa BBbbbbbb GGGggggg RRRrrrrr */
if (backward_compatible) {
Py_UInt32 value = * (Py_UInt32 *) cp;
cp += 4;
r = (int) ((value & 0xff) / 255. * 7. + .5);
g = (int) (((value >> 8) & 0xff) / 255. * 7. + .5);
b = (int) (((value >> 16) & 0xff) / 255. * 3. + .5);
} else {
cp++; /* skip alpha channel */
b = (int) (*cp++ / 255. * 3. + .5);
g = (int) (*cp++ / 255. * 7. + .5);
r = (int) (*cp++ / 255. * 7. + .5);
}
*ncp++ = (unsigned char)((r<<5) | (b<<3) | g);
}
return rv;
}
static PyObject *
imageop_rgb82rgb(PyObject *self, PyObject *args)
{
int x, y, len, nlen;
unsigned char *cp;
unsigned char *ncp;
PyObject *rv;
int i, r, g, b;
unsigned char value;
int backward_compatible = imageop_backward_compatible();
if ( !PyArg_ParseTuple(args, "s#ii", &cp, &len, &x, &y) )
return 0;
nlen = x*y;
if ( nlen != len ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, nlen*4);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_AsString(rv);
for ( i=0; i < nlen; i++ ) {
/* Bits in source: RRRBBGGG
** Red and Green are multiplied by 36.5, Blue by 85
*/
value = *cp++;
r = (value >> 5) & 7;
g = (value ) & 7;
b = (value >> 3) & 3;
r = (r<<5) | (r<<3) | (r>>1);
g = (g<<5) | (g<<3) | (g>>1);
b = (b<<6) | (b<<4) | (b<<2) | b;
if (backward_compatible) {
Py_UInt32 nvalue = r | (g<<8) | (b<<16);
* (Py_UInt32 *) ncp = nvalue;
ncp += 4;
} else {
*ncp++ = 0;
*ncp++ = b;
*ncp++ = g;
*ncp++ = r;
}
}
return rv;
}
static PyObject *
imageop_rgb2grey(PyObject *self, PyObject *args)
{
int x, y, len, nlen;
unsigned char *cp;
unsigned char *ncp;
PyObject *rv;
int i, r, g, b;
int nvalue;
int backward_compatible = imageop_backward_compatible();
if ( !PyArg_ParseTuple(args, "s#ii", &cp, &len, &x, &y) )
return 0;
nlen = x*y;
if ( nlen*4 != len ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, nlen);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_AsString(rv);
for ( i=0; i < nlen; i++ ) {
if (backward_compatible) {
Py_UInt32 value = * (Py_UInt32 *) cp;
cp += 4;
r = (int) ((value & 0xff) / 255. * 7. + .5);
g = (int) (((value >> 8) & 0xff) / 255. * 7. + .5);
b = (int) (((value >> 16) & 0xff) / 255. * 3. + .5);
} else {
cp++; /* skip alpha channel */
b = *cp++;
g = *cp++;
r = *cp++;
}
nvalue = (int)(0.30*r + 0.59*g + 0.11*b);
if ( nvalue > 255 ) nvalue = 255;
*ncp++ = (unsigned char)nvalue;
}
return rv;
}
static PyObject *
imageop_grey2rgb(PyObject *self, PyObject *args)
{
int x, y, len, nlen;
unsigned char *cp;
unsigned char *ncp;
PyObject *rv;
int i;
unsigned char value;
int backward_compatible = imageop_backward_compatible();
if ( !PyArg_ParseTuple(args, "s#ii", &cp, &len, &x, &y) )
return 0;
nlen = x*y;
if ( nlen != len ) {
PyErr_SetString(ImageopError, "String has incorrect length");
return 0;
}
rv = PyString_FromStringAndSize(NULL, nlen*4);
if ( rv == 0 )
return 0;
ncp = (unsigned char *)PyString_AsString(rv);
for ( i=0; i < nlen; i++ ) {
value = *cp++;
if (backward_compatible) {
* (Py_UInt32 *) ncp = (Py_UInt32) value | ((Py_UInt32) value << 8 ) | ((Py_UInt32) value << 16);
ncp += 4;
} else {
*ncp++ = 0;
*ncp++ = value;
*ncp++ = value;
*ncp++ = value;
}
}
return rv;
}
/*
static object *
imageop_mul(object *self, object *args)
{
char *cp, *ncp;
int len, size, x, y;
object *rv;
int i;
if ( !getargs(args, "(s#iii)", &cp, &len, &size, &x, &y) )
return 0;
if ( size != 1 && size != 4 ) {
err_setstr(ImageopError, "Size should be 1 or 4");
return 0;
}
if ( len != size*x*y ) {
err_setstr(ImageopError, "String has incorrect length");
return 0;
}
rv = newsizedstringobject(NULL, XXXX);
if ( rv == 0 )
return 0;
ncp = (char *)getstringvalue(rv);
for ( i=0; i < len; i += size ) {
}
return rv;
}
*/
static PyMethodDef imageop_methods[] = {
{ "crop", imageop_crop, METH_VARARGS },
{ "scale", imageop_scale, METH_VARARGS },
{ "grey2mono", imageop_grey2mono, METH_VARARGS },
{ "grey2grey2", imageop_grey2grey2, METH_VARARGS },
{ "grey2grey4", imageop_grey2grey4, METH_VARARGS },
{ "dither2mono", imageop_dither2mono, METH_VARARGS },
{ "dither2grey2", imageop_dither2grey2, METH_VARARGS },
{ "mono2grey", imageop_mono2grey, METH_VARARGS },
{ "grey22grey", imageop_grey22grey, METH_VARARGS },
{ "grey42grey", imageop_grey42grey, METH_VARARGS },
{ "tovideo", imageop_tovideo, METH_VARARGS },
{ "rgb2rgb8", imageop_rgb2rgb8, METH_VARARGS },
{ "rgb82rgb", imageop_rgb82rgb, METH_VARARGS },
{ "rgb2grey", imageop_rgb2grey, METH_VARARGS },
{ "grey2rgb", imageop_grey2rgb, METH_VARARGS },
{ 0, 0 }
};
PyMODINIT_FUNC
initimageop(void)
{
PyObject *m;
m = Py_InitModule("imageop", imageop_methods);
ImageopDict = PyModule_GetDict(m);
ImageopError = PyErr_NewException("imageop.error", NULL, NULL);
if (ImageopError != NULL)
PyDict_SetItemString(ImageopDict, "error", ImageopError);
}
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