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#define PERL_NO_GET_CONTEXT
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"
#include <stdlib.h>
#include <stdint.h>
int paeth_predictor (int a, int b, int c) {
int p = a + b - c;
int pa = abs(p - a);
int pb = abs(p - b);
int pc = abs(p - c);
if ((pa <= pb ) && (pa <= pc)) {
return a;
}
else if (pb <= pc) {
return b;
}
else {
return c;
}
}
MODULE = PDF::API2::XS::ImagePNG PACKAGE = PDF::API2::XS::ImagePNG
PROTOTYPES: DISABLE
AV*
unfilter (AV * line, AV * prev, int filter, int bpp)
CODE:
int line_length = av_len(line);
uint8_t * in_array = (uint8_t *)malloc((line_length) * sizeof(uint8_t));
uint8_t * prev_array = (uint8_t *)malloc((line_length) * sizeof(uint8_t));
uint8_t * out_array = (uint8_t *)malloc((line_length) * sizeof(uint8_t));
if (in_array == NULL || out_array == NULL || prev_array == NULL) {
croak("Null pointer from memory allocation in ImagePNG.xs");
}
for (int i = 0; i < line_length; i++) {
SV** elem = av_fetch(line, i, 0);
char * ptr = SvPV_nolen(*elem);
uint8_t byte = (uint8_t) *ptr;
*(in_array + i) = byte;
}
for (int i = 0; i < line_length; i++) {
uint8_t byte;
SV** elem = av_fetch(prev, i, 0);
if (elem != NULL) {
char * ptr = SvPV_nolen(*elem);
byte = (uint8_t) *ptr;
}
else {
byte = 0;
}
*(prev_array + i) = byte;
}
switch (filter) {
case 0 :
for (int i = 0; i < line_length; i++) {
*(out_array + i) = *(in_array + i);
}
break;
case 1 :
for (int i = 0; i < line_length; i++) {
uint8_t sub;
if (i < bpp) {
sub = *(in_array + i);
}
else {
sub = *(in_array + i) + *(out_array + i - bpp);
}
*(out_array + i) = sub;
}
break;
case 2 :
for (int i = 0; i < line_length; i++) {
*(out_array + i) = *(in_array + i) + *(prev_array + i);
}
break;
case 3 :
for (int i = 0; i < line_length; i++) {
uint8_t sub;
if (i < bpp) {
sub = *(in_array + i) + (*(prev_array + i) / 2);
}
else {
sub = *(in_array + i) + ((*(out_array + i - bpp) + *(prev_array + i)) / 2);
}
*(out_array + i) = sub;
}
break;
case 4 :
for (int i = 0; i < line_length; i++) {
uint8_t a, b, c;
b = *(prev_array + i);
if (i < bpp) {
a = 0;
c = 0;
}
else {
a = *(out_array + i - bpp);
c = *(prev_array + i - bpp);
}
*(out_array + i) = *(in_array + i) + paeth_predictor(a, b, c);
}
break;
}
// Put the results back into a new Perl AV.
AV * clearstream_av = newAV();
for (int i = 0; i < (line_length); i++) {
SV * this_sv = newSVuv(*(out_array + i));
av_push(clearstream_av, this_sv);
}
free(in_array);
free(out_array);
free(prev_array);
RETVAL = clearstream_av;
OUTPUT:
RETVAL
AV*
split_channels (AV * stream, int w, int h)
CODE:
//
// The image is passed as a Perl AV (Array Variable).
//
// It cannot be passed in as a regular C char string
// or converted to a regular C char string because
// it gets truncated at the first zero byte.
//
// First we need to turn it into a C array of bytes.
// av_len, av_fetch and SvPV_nolen are XS macros.
// See documentation here: https://perldoc.perl.org/perlguts.html
//
uint8_t * in_array = (uint8_t *)malloc((w * h * 4) * sizeof(uint8_t));
uint8_t * out_array = (uint8_t *)malloc((w * h * 4) * sizeof(uint8_t));
uint8_t * dict_array = (uint8_t *)malloc((w * h) * sizeof(uint8_t));
if (in_array == NULL || out_array == NULL || dict_array == NULL) {
croak("Null pointer from memory allocation in ImagePNG.xs");
}
for (int i = 0; i < av_len(stream); i++) {
SV** elem = av_fetch(stream, i, 0);
char * ptr = SvPV_nolen(*elem);
uint8_t byte = (uint8_t) *ptr;
*(in_array + i) = byte;
}
// Transform the image into a new C array of bytes.
for (int i = 0; i < w * h; i++) {
*(out_array + (i * 3) + 0) = *(in_array + (i * 4) + 0);
*(out_array + (i * 3) + 1) = *(in_array + (i * 4) + 1);
*(out_array + (i * 3) + 2) = *(in_array + (i * 4) + 2);
*(dict_array + i) = *(in_array + (i * 4) + 3);
}
// Put the results back into a new Perl AV.
AV * outstream_av = newAV();
for (int i = 0; i < (w * h * 3); i++) {
SV * this_sv = newSVuv(*(out_array + i));
av_push(outstream_av, this_sv);
}
for (int i = 0; i < (w * h * 3); i++) {
SV * this_sv = newSVuv(*(dict_array + i));
av_push(outstream_av, this_sv);
}
free(in_array);
free(out_array);
free(dict_array);
// Send the transformed image back to Perl in the new AV.
RETVAL = outstream_av;
OUTPUT:
RETVAL
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