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#include <fitz.h>
/* TODO: check if this works with 16bpp images */
enum { MAXC = 16 };
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 *ref;
int encode;
};
fz_error *
fz_newpredict(fz_filter **fp, fz_obj *params, int encode)
{
fz_obj *obj;
FZ_NEWFILTER(fz_predict, p, predict);
p->encode = encode;
p->predictor = 1;
p->columns = 1;
p->colors = 1;
p->bpc = 8;
obj = fz_dictgets(params, "Predictor");
if (obj) p->predictor = fz_toint(obj);
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->ref = fz_malloc(p->stride);
if (!p->ref) { fz_free(p); return fz_outofmem; }
memset(p->ref, 0, p->stride);
}
else {
p->ref = nil;
}
return nil;
}
void
fz_droppredict(fz_filter *filter)
{
fz_predict *p = (fz_predict*)filter;
fz_free(p->ref);
}
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 = (ac < 0 ? -ac : ac);
int pb = (bc < 0 ? -bc : bc);
int pc = (abcc < 0 ? -abcc : abcc);
return pa <= pb && pa <= pc ? a : pb <= pc ? b : c;
}
static inline void
none(fz_predict *p, unsigned char *in, unsigned char *out)
{
memcpy(out, in, p->stride);
}
static void
tiff(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 = p->encode ? a - left[k] : a + left[k];
int c = b % (1 << p->bpc);
putcomponent(out, i * p->colors + k, p->bpc, c);
left[k] = p->encode ? a : c;
}
}
}
static void
png(fz_predict *p, unsigned char *in, unsigned char *out, int predictor)
{
int upleft[MAXC], left[MAXC], i, k;
for (k = 0; k < p->bpp; k++) {
left[k] = 0;
upleft[k] = 0;
}
if (p->encode)
{
for (k = 0, i = 0; i < p->stride; k = (k + 1) % p->bpp, i ++)
{
switch (predictor)
{
case 0: out[i] = in[i]; break;
case 1: out[i] = in[i] - left[k]; break;
case 2: out[i] = in[i] - p->ref[i]; break;
case 3: out[i] = in[i] - (left[k] + p->ref[i]) / 2; break;
case 4: out[i] = in[i] - paeth(left[k], p->ref[i], upleft[k]); break;
}
left[k] = in[i];
upleft[k] = p->ref[i];
}
}
else
{
for (k = 0, i = 0; i < p->stride; k = (k + 1) % p->bpp, i ++)
{
switch (predictor)
{
case 0: out[i] = in[i]; break;
case 1: out[i] = in[i] + left[k]; break;
case 2: out[i] = in[i] + p->ref[i]; break;
case 3: out[i] = in[i] + (left[k] + p->ref[i]) / 2; break;
case 4: out[i] = in[i] + paeth(left[k], p->ref[i], upleft[k]); break;
}
left[k] = out[i];
upleft[k] = p->ref[i];
}
}
}
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;
while (1)
{
if (in->rp + dec->stride + (!dec->encode && ispng) > in->wp) {
if (in->eof)
return fz_iodone;
return fz_ioneedin;
}
if (out->wp + dec->stride + (dec->encode && ispng) > out->ep)
return fz_ioneedout;
if (dec->predictor == 1) {
none(dec, in->rp, out->wp);
}
else if (dec->predictor == 2) {
if (dec->bpc != 8)
memset(out->wp, 0, dec->stride);
tiff(dec, in->rp, out->wp);
}
else {
if (dec->encode) {
predictor = dec->predictor - 10;
if (predictor < 0 || predictor > 4)
predictor = 1;
*out->wp ++ = predictor;
}
else {
predictor = *in->rp++;
}
png(dec, in->rp, out->wp, predictor);
}
if (dec->ref)
memcpy(dec->ref, out->wp, dec->stride);
in->rp += dec->stride;
out->wp += dec->stride;
}
}
fz_error *
fz_newpredictd(fz_filter **fp, fz_obj *params)
{
return fz_newpredict(fp, params, 0);
}
fz_error *
fz_newpredicte(fz_filter **fp, fz_obj *params)
{
return fz_newpredict(fp, params, 1);
}
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