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#include "fitz.h"
/* TODO: check if this works with 16bpp images */
enum { MAXC = 32 };
typedef struct fz_predict_s fz_predict;
struct fz_predict_s
{
fz_filter super;
int predictor;
int columns;
int colors;
int bpc;
int stride;
int bpp;
unsigned char *refbuf;
unsigned char *ref;
};
fz_filter *
fz_newpredictd(fz_obj *params)
{
fz_obj *obj;
FZ_NEWFILTER(fz_predict, p, predict);
p->predictor = 1;
p->columns = 1;
p->colors = 1;
p->bpc = 8;
obj = fz_dictgets(params, "Predictor");
if (obj)
p->predictor = fz_toint(obj);
if (p->predictor != 1 && p->predictor != 2 &&
p->predictor != 10 && p->predictor != 11 &&
p->predictor != 12 && p->predictor != 13 &&
p->predictor != 14 && p->predictor != 15)
{
fz_warn("invalid predictor: %d", p->predictor);
p->predictor = 1;
}
obj = fz_dictgets(params, "Columns");
if (obj)
p->columns = fz_toint(obj);
obj = fz_dictgets(params, "Colors");
if (obj)
p->colors = fz_toint(obj);
obj = fz_dictgets(params, "BitsPerComponent");
if (obj)
p->bpc = fz_toint(obj);
p->stride = (p->bpc * p->colors * p->columns + 7) / 8;
p->bpp = (p->bpc * p->colors + 7) / 8;
if (p->predictor >= 10)
{
p->refbuf = fz_malloc(p->stride);
memset(p->refbuf, 0, p->stride);
}
else
{
p->refbuf = nil;
}
p->ref = nil;
return (fz_filter*)p;
}
void
fz_droppredict(fz_filter *filter)
{
fz_predict *p = (fz_predict*)filter;
fz_free(p->refbuf);
}
static inline int
getcomponent(unsigned char *buf, int x, int bpc)
{
switch (bpc)
{
case 1: return buf[x / 8] >> (7 - (x % 8)) & 0x01;
case 2: return buf[x / 4] >> ((3 - (x % 4)) * 2) & 0x03;
case 4: return buf[x / 2] >> ((1 - (x % 2)) * 4) & 0x0f;
case 8: return buf[x];
}
return 0;
}
static inline void
putcomponent(unsigned char *buf, int x, int bpc, int value)
{
switch (bpc)
{
case 1: buf[x / 8] |= value << (7 - (x % 8)); break;
case 2: buf[x / 4] |= value << ((3 - (x % 4)) * 2); break;
case 4: buf[x / 2] |= value << ((1 - (x % 2)) * 4); break;
case 8: buf[x] = value; break;
}
}
static inline int
paeth(int a, int b, int c)
{
/* The definitions of ac and bc are correct, not a typo. */
int ac = b - c, bc = a - c, abcc = ac + bc;
int pa = ABS(ac);
int pb = ABS(bc);
int pc = ABS(abcc);
return pa <= pb && pa <= pc ? a : pb <= pc ? b : c;
}
static inline void
fz_predictnone(fz_predict *p, unsigned char *in, unsigned char *out)
{
memcpy(out, in, p->stride);
}
static void
fz_predicttiff(fz_predict *p, unsigned char *in, unsigned char *out)
{
int left[MAXC];
int i, k;
for (k = 0; k < p->colors; k++)
left[k] = 0;
for (i = 0; i < p->columns; i++)
{
for (k = 0; k < p->colors; k++)
{
int a = getcomponent(in, i * p->colors + k, p->bpc);
int b = a + left[k];
int c = b % (1 << p->bpc);
putcomponent(out, i * p->colors + k, p->bpc, c);
left[k] = c;
}
}
}
static void
fz_predictpng(fz_predict *p, unsigned char *in, unsigned char *out, int predictor)
{
int bpp = p->bpp;
int i;
unsigned char *ref = p->ref;
switch (predictor)
{
case 0:
memcpy(out, in, p->stride);
break;
case 1:
for (i = bpp; i > 0; i--)
{
*out++ = *in++;
}
for (i = p->stride - bpp; i > 0; i--)
{
*out = *in++ + out[-bpp];
out++;
}
break;
case 2:
for (i = bpp; i > 0; i--)
{
*out++ = *in++ + *ref++;
}
for (i = p->stride - bpp; i > 0; i--)
{
*out++ = *in++ + *ref++;
}
break;
case 3:
for (i = bpp; i > 0; i--)
{
*out++ = *in++ + (*ref++) / 2;
}
for (i = p->stride - bpp; i > 0; i--)
{
*out = *in++ + (out[-bpp] + *ref++)/2;
out++;
}
break;
case 4:
for (i = bpp; i > 0; i--)
{
*out++ = *in++ + paeth(0, *ref++, 0);
}
for (i = p->stride - bpp; i > 0; i --)
{
*out = *in++ + paeth(out[-bpp], *ref, ref[-bpp]);
ref++;
out++;
}
break;
}
}
fz_error
fz_processpredict(fz_filter *filter, fz_buffer *in, fz_buffer *out)
{
fz_predict *dec = (fz_predict*)filter;
int ispng = dec->predictor >= 10;
int predictor;
dec->ref = dec->refbuf;
while (1)
{
if (in->rp + dec->stride + ispng > in->wp)
{
if (in->eof)
return fz_iodone;
if (dec->refbuf != dec->ref)
{
memcpy(dec->refbuf, dec->ref, dec->stride);
}
return fz_ioneedin;
}
if (out->wp + dec->stride > out->ep)
{
if (dec->refbuf != dec->ref)
{
memcpy(dec->refbuf, dec->ref, dec->stride);
}
return fz_ioneedout;
}
if (dec->predictor == 1)
{
fz_predictnone(dec, in->rp, out->wp);
}
else if (dec->predictor == 2)
{
if (dec->bpc != 8)
memset(out->wp, 0, dec->stride);
fz_predicttiff(dec, in->rp, out->wp);
}
else
{
predictor = *in->rp++;
fz_predictpng(dec, in->rp, out->wp, predictor);
}
if (dec->refbuf)
{
dec->ref = out->wp;
}
in->rp += dec->stride;
out->wp += dec->stride;
}
}
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