/*
** returns the index of a `key' for table traversals. First goes all
** elements in the array part, then elements in the hash part. The
** beginning of a traversal is signalled by -1.
*/
static int findindex (lua_State *L, Table *t, StkId key) {
int i;
if (ttisnil(key)) return -1; /* first iteration */
i = arrayindex(key);
if (0 < i && i <= t->sizearray) /* is `key' inside array part? */
return i-1; /* yes; that's the index (corrected to C) */
else {
Node *n = mainposition(t, key);
do { /* check whether `key' is somewhere in the chain */
/* key may be dead already, but it is ok to use it in `next' */
if (luaO_rawequalObj(key2tval(n), key) ||
(ttype(gkey(n)) == LUA_TDEADKEY && iscollectable(key) &&
gcvalue(gkey(n)) == gcvalue(key))) {
i = cast_int(n - gnode(t, 0)); /* key index in hash table */
/* hash elements are numbered after array ones */
return i + t->sizearray;
}
else n = gnext(n);
} while (n);
luaG_runerror(L, "invalid key to " LUA_QL("next")); /* key not found */
return 0; /* to avoid warnings */
}
}
static int countint (const TValue *key, int *nums) {
int k = arrayindex(key,MAXASIZE);
if (k>0) { /* appropriate array index? */
nums[ceillog2( cast(unsigned int,k) )]++; /* count as such */
return 1;
}
static PyObject *
dither(PyObject *self, PyObject *args) {
/*
*
*/
// params
int w, h, type, treshhold;
// iterators
int x, y;
// calculated array index
int idx;
int count;
ERRBUFTYPE *errorBuffer, errdiv, newval, errval;
const unsigned char *sourceImage;
unsigned char *resultImage;
PyObject *result;
if (!PyArg_ParseTuple(args, "s#iiii", &sourceImage, &count, &w, &h, &type, &treshhold)) {
return (NULL);
}
// create the buffers
resultImage = (unsigned char *)malloc( count );
errorBuffer = (ERRBUFTYPE *)malloc( count*sizeof(ERRBUFTYPE));
// init & check the buffers
memcpy( (void *)resultImage, (const void *)sourceImage, count);
memset( errorBuffer, 0, count*sizeof(ERRBUFTYPE));
if (!resultImage) {
PyErr_NoMemory();
return NULL;
}
if (!errorBuffer) {
PyErr_NoMemory();
return NULL;
}
// iterate over all pixels (x,y)
for (y = 0; y < h; y++) {
for (x = 0; x < w; x++) {
// calc array index for image and error buffers
idx = arrayindex(x, y, w);
newval = errorBuffer[idx] + resultImage[idx];
// set pixel value
if (newval >= treshhold) {
errval = newval - 255;
errdiv = errval / 8;
resultImage[idx] = 255;
} else {
errval = newval;
errdiv = errval / 8;
resultImage[idx] = 0;
}
// cut short if nothing to add
if (errdiv == 0)
continue;
distributeError( x, y, w, h, type, errval, resultImage, errorBuffer);
}
}
// build the return value
result = Py_BuildValue("s#", resultImage, count);
free(errorBuffer);
free(resultImage);
return result;
}
static void distributeError( int x, int y,
int w, int h,
int type,
ERRBUFTYPE errval,
unsigned char destImage[], ERRBUFTYPE errorBuffer[] ) {
/*
* Distribute the error to neighbouring pixels.
*
* The distributions have been taken from
*
* http://www.tannerhelland.com/4660/dithering-eleven-algorithms-source-code/
*
*
* The errors are mine. kw 2018-01
*/
ERRBUFTYPE errdiv1, errdiv2, errdiv3, errdiv4;
int idx;
if (type < 0) {
type = 0;
}
if (type >= zzsentinel) {
type = zzsentinel-1;
}
switch (type){
case atkinsondither:
// distribute the error
// atkinson dithering divides by eight but distributes only 6/8
errdiv1 = errval / (UNIT * 8);
if ( x+1 < w ) {
// x+1 ,y
idx = arrayindex(x+1, y, w);
errorBuffer[idx] += errdiv1;
if ( x+2 < w ) {
// x+2 ,y
idx = arrayindex(x+2, y, w);
errorBuffer[idx] += errdiv1;
}
}
if ( y+1 < h ) {
// x ,y+1
idx = arrayindex(x, y+1, w);
errorBuffer[idx] += errdiv1;
if (x-1 >= 0) {
// x-1, y+1
idx = arrayindex(x-1, y+1, w);
errorBuffer[idx] += errdiv1;
}
if ( y+2 < h ) {
// x, y+2
idx = arrayindex(x, y+2, w);
errorBuffer[idx] += errdiv1;
}
if (x+1 < w) {
// x+1, y+1
idx = arrayindex(x+1, y+1, w);
errorBuffer[idx] += errdiv1;
}
}
break;
case floydsteinbergdither:
errdiv1 = errval / (UNIT * 16) * 7;
errdiv2 = errval / (UNIT * 16) * 3;
errdiv3 = errval / (UNIT * 16) * 5;
errdiv4 = errval / (UNIT * 16) * 1;
if ( x+1 < w ) {
// x+1 ,y
idx = arrayindex(x+1, y, w);
// 7/16
errorBuffer[idx] += errdiv1;
if ( y+1 < h ) {
// x+1 ,y+1
idx = arrayindex(x+1, y+1, w);
// 1/16
errorBuffer[idx] += errdiv4;
}
}
if ( y+1 < h ) {
// x ,y+1
idx = arrayindex(x, y+1, w);
// 5/16
errorBuffer[idx] += errdiv3;
if (x > 0) {
// x-1 ,y+1
idx = arrayindex(x-1, y+1, w);
// 3/16
errorBuffer[idx] += errdiv2;
}
}
break;
case jarvisjudiceninkedithering:
errdiv1 = errval / (UNIT * 48) * 7;
errdiv2 = errval / (UNIT * 48) * 5;
errdiv3 = errval / (UNIT * 48) * 3;
errdiv4 = errval / (UNIT * 48) * 1;
if ( x+1 < w ) {
// x+1 ,y
idx = arrayindex(x+1, y, w);
// 7/48
errorBuffer[idx] += errdiv1;
if ( y+1 < h ) {
// x+1 ,y+1
idx = arrayindex(x+1, y+1, w);
// 5/48
errorBuffer[idx] += errdiv2;
}
if ( y+2 < h ) {
// x+1 ,y+2
idx = arrayindex(x+1, y+2, w);
// 3/48
errorBuffer[idx] += errdiv3;
}
if ( x+2 < w ) {
// x+2 ,y
idx = arrayindex(x+2, y, w);
// 5/48
errorBuffer[idx] += errdiv2;
if ( y+1 < h ) {
// x+2 ,y+1
idx = arrayindex(x+2, y+1, w);
// 3/48
errorBuffer[idx] += errdiv3;
}
if ( y+2 < h ) {
// x+2 ,y+2
idx = arrayindex(x+2, y+2, w);
// 1/48
errorBuffer[idx] += errdiv4;
}
}
}
if (y+1 < h) {
// x, y+1
idx = arrayindex(x, y+1, w);
// 7/48
errorBuffer[idx] += errdiv1;
}
if (y+2 < h) {
// x, y+2
idx = arrayindex(x, y+2, w);
// 5/48
errorBuffer[idx] += errdiv2;
}
if ( x-1 > 0 ) {
if (y+1 < h) {
// x-1, y+1
idx = arrayindex(x-1, y+1, w);
// 5/48
errorBuffer[idx] += errdiv2;
}
if (y+2 < h) {
// x-1, y+2
idx = arrayindex(x-1, y+2, w);
// 3/48
errorBuffer[idx] += errdiv3;
}
}
if ( x-2 > 0 ) {
if (y+1 < h) {
// x-2, y+1
idx = arrayindex(x-2, y+1, w);
// 3/48
errorBuffer[idx] += errdiv3;
}
if (y+2 < h) {
// x-2, y+2
idx = arrayindex(x-2, y+2, w);
// 1/48
errorBuffer[idx] += errdiv4;
}
}
break;
case stuckidithering:
errdiv1 = errval / (UNIT * 42) * 8;
errdiv2 = errval / (UNIT * 42) * 4;
errdiv3 = errval / (UNIT * 42) * 2;
errdiv4 = errval / (UNIT * 42) * 1;
if ( x+1 < w ) {
// x+1 ,y
idx = arrayindex(x+1, y, w);
// 8/42
errorBuffer[idx] += errdiv1;
if ( y+1 < h ) {
// x+1, y+1
idx = arrayindex(x+1, y+1, w);
// 4/42
errorBuffer[idx] += errdiv2;
}
if ( y+2 < h ) {
// x+1, y+2
idx = arrayindex(x+1, y+2, w);
// 2/42
errorBuffer[idx] += errdiv3;
}
if ( x+2 < w ) {
// x+2 ,y
idx = arrayindex(x+2, y, w);
// 4/42
errorBuffer[idx] += errdiv2;
if ( y+1 < h ) {
// x+2, y+1
idx = arrayindex(x+2, y+1, w);
// 2/42
errorBuffer[idx] += errdiv3;
}
if ( y+2 < h ) {
// x+2, y+2
idx = arrayindex(x+2, y+2, w);
// 1/42
errorBuffer[idx] += errdiv4;
}
}
}
if (y+1 < h) {
if (x-2 > 0) {
idx = arrayindex(x-2, y+1, w);
// 2/42
errorBuffer[idx] += errdiv3;
}
if (x-1 > 0) {
idx = arrayindex(x-1, y+1, w);
// 4/42
errorBuffer[idx] += errdiv2;
}
idx = arrayindex(x, y+1, w);
// 8/42
errorBuffer[idx] += errdiv1;
}
if (y+2 < h) {
if (x-2 > 0) {
idx = arrayindex(x-2, y+2, w);
// 1/42
errorBuffer[idx] += errdiv4;
}
if (x-1 > 0) {
idx = arrayindex(x-1, y+2, w);
// 2/42
errorBuffer[idx] += errdiv2;
}
idx = arrayindex(x, y+2, w);
// 4/42
errorBuffer[idx] += errdiv2;
}
break;
case burkesdithering:
errdiv1 = errval / (UNIT * 32) * 8;
errdiv2 = errval / (UNIT * 32) * 4;
errdiv3 = errval / (UNIT * 32) * 2;
if ( x+1 < w ) {
// x+1 ,y
idx = arrayindex(x+1, y, w);
// 8/32
errorBuffer[idx] += errdiv1;
if ( y+1 < h ) {
// x+1, y+1
idx = arrayindex(x+1, y+1, w);
// 4/32
errorBuffer[idx] += errdiv2;
}
if ( x+2 < w ) {
// x+2 ,y
idx = arrayindex(x+2, y, w);
// 4/32
errorBuffer[idx] += errdiv2;
if ( y+1 < h ) {
// x+2, y+1
idx = arrayindex(x+2, y+1, w);
// 2/32
errorBuffer[idx] += errdiv3;
}
}
}
if (y+1 < h) {
if (x-2 > 0) {
idx = arrayindex(x-2, y+1, w);
// 2/32
errorBuffer[idx] += errdiv3;
}
if (x-1 > 0) {
idx = arrayindex(x-1, y+1, w);
// 4/32
errorBuffer[idx] += errdiv2;
}
idx = arrayindex(x, y+1, w);
// 8/32
errorBuffer[idx] += errdiv1;
}
break;
case sierra1dithering:
errdiv1 = errval / (UNIT * 32) * 5;
errdiv2 = errval / (UNIT * 32) * 4;
errdiv3 = errval / (UNIT * 32) * 3;
errdiv4 = errval / (UNIT * 32) * 2;
if ( x+1 < w ) {
// x+1 ,y
idx = arrayindex(x+1, y, w);
// 5/32
errorBuffer[idx] += errdiv1;
if ( y+1 < h ) {
// x+1, y+1
idx = arrayindex(x+1, y+1, w);
// 4/32
errorBuffer[idx] += errdiv2;
}
if ( y+2 < h ) {
// x+1, y+2
idx = arrayindex(x+1, y+2, w);
// 2/32
errorBuffer[idx] += errdiv4;
}
if ( x+2 < w ) {
// x+2 ,y
idx = arrayindex(x+2, y, w);
// 3/16
errorBuffer[idx] += errdiv3;
if ( y+1 < h ) {
// x+2, y+1
idx = arrayindex(x+2, y+1, w);
// 2/16
errorBuffer[idx] += errdiv4;
}
}
}
if (y+1 < h) {
if (x-2 > 0) {
idx = arrayindex(x-2, y+1, w);
// 2/32
errorBuffer[idx] += errdiv4;
}
if (x-1 > 0) {
idx = arrayindex(x-1, y+1, w);
// 4/32
errorBuffer[idx] += errdiv2;
}
idx = arrayindex(x, y+1, w);
// 5/32
errorBuffer[idx] += errdiv1;
}
if (y+2 < h) {
if (x-1 > 0) {
idx = arrayindex(x-1, y+2, w);
// 2/32
errorBuffer[idx] += errdiv4;
}
if (x+1 < w) {
idx = arrayindex(x+1, y+2, w);
// 2/32
errorBuffer[idx] += errdiv4;
}
idx = arrayindex(x, y+2, w);
// 3/32
errorBuffer[idx] += errdiv3;
}
break;
case sierra2dithering:
errdiv1 = errval / (UNIT * 16) * 4;
errdiv2 = errval / (UNIT * 16) * 3;
errdiv3 = errval / (UNIT * 16) * 2;
errdiv4 = errval / (UNIT * 16) * 1;
if ( x+1 < w ) {
// x+1 ,y
idx = arrayindex(x+1, y, w);
// 4/16
errorBuffer[idx] += errdiv1;
if ( y+1 < h ) {
// x+1, y+1
idx = arrayindex(x+1, y+1, w);
// 2/16
errorBuffer[idx] += errdiv2;
}
if ( x+2 < w ) {
// x+2 ,y
idx = arrayindex(x+2, y, w);
// 3/16
errorBuffer[idx] += errdiv2;
if ( y+1 < h ) {
// x+2, y+1
idx = arrayindex(x+2, y+1, w);
// 1/16
errorBuffer[idx] += errdiv4;
}
}
}
if (y+1 < h) {
if (x-2 > 0) {
idx = arrayindex(x-2, y+1, w);
// 1/16
errorBuffer[idx] += errdiv4;
}
if (x-1 > 0) {
idx = arrayindex(x-1, y+1, w);
// 2/16
errorBuffer[idx] += errdiv3;
}
idx = arrayindex(x, y+1, w);
// 3/16
errorBuffer[idx] += errdiv2;
}
break;
case sierra3dithering:
errdiv1 = errval / (UNIT * 4) * 2;
errdiv2 = errval / (UNIT * 4) * 1;
if ( x+1 < w ) {
// x+1 ,y
idx = arrayindex(x+1, y, w);
// 2/4
errorBuffer[idx] += errdiv1;
}
if ( y+1 < h ) {
// x, y+1
idx = arrayindex(x, y+1, w);
// 1/4
errorBuffer[idx] += errdiv2;
if ( x-1 > 0 ) {
// x-1, y+1
idx = arrayindex(x-1, y+1, w);
// 1/4
errorBuffer[idx] += errdiv2;
}
}
break;
}
}
