Pl_PNGFilter.cc
2.84 KB
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#include <qpdf/Pl_PNGFilter.hh>
#include <stdexcept>
#include <string.h>
#include <limits.h>
Pl_PNGFilter::Pl_PNGFilter(char const* identifier, Pipeline* next,
action_e action, unsigned int columns,
unsigned int bytes_per_pixel) :
Pipeline(identifier, next),
action(action),
columns(columns),
cur_row(0),
prev_row(0),
buf1(0),
buf2(0),
pos(0)
{
if ((columns == 0) || (columns > UINT_MAX - 1))
{
throw std::runtime_error(
"PNGFilter created with invalid columns value");
}
this->buf1 = new unsigned char[columns + 1];
this->buf2 = new unsigned char[columns + 1];
this->cur_row = buf1;
// number of bytes per incoming row
this->incoming = (action == a_encode ? columns : columns + 1);
}
Pl_PNGFilter::~Pl_PNGFilter()
{
delete [] buf1;
delete [] buf2;
}
void
Pl_PNGFilter::write(unsigned char* data, size_t len)
{
size_t left = this->incoming - this->pos;
size_t offset = 0;
while (len >= left)
{
// finish off current row
memcpy(this->cur_row + this->pos, data + offset, left);
offset += left;
len -= left;
processRow();
// Swap rows
unsigned char* t = this->prev_row;
this->prev_row = this->cur_row;
this->cur_row = t ? t : this->buf2;
memset(this->cur_row, 0, this->columns + 1);
left = this->incoming;
this->pos = 0;
}
if (len)
{
memcpy(this->cur_row + this->pos, data + offset, len);
}
this->pos += len;
}
void
Pl_PNGFilter::processRow()
{
if (this->action == a_encode)
{
encodeRow();
}
else
{
decodeRow();
}
}
void
Pl_PNGFilter::decodeRow()
{
int filter = this->cur_row[0];
if (this->prev_row)
{
switch (filter)
{
case 0: // none
break;
case 1: // sub
throw std::logic_error("sub filter not implemented");
break;
case 2: // up
for (unsigned int i = 1; i <= this->columns; ++i)
{
this->cur_row[i] += this->prev_row[i];
}
break;
case 3: // average
throw std::logic_error("average filter not implemented");
break;
case 4: // Paeth
throw std::logic_error("Paeth filter not implemented");
break;
default:
// ignore
break;
}
}
getNext()->write(this->cur_row + 1, this->columns);
}
void
Pl_PNGFilter::encodeRow()
{
// For now, hard-code to using UP filter.
unsigned char ch = 2;
getNext()->write(&ch, 1);
if (this->prev_row)
{
for (unsigned int i = 0; i < this->columns; ++i)
{
ch = this->cur_row[i] - this->prev_row[i];
getNext()->write(&ch, 1);
}
}
else
{
getNext()->write(this->cur_row, this->columns);
}
}
void
Pl_PNGFilter::finish()
{
if (this->pos)
{
// write partial row
processRow();
}
this->prev_row = 0;
this->cur_row = buf1;
this->pos = 0;
memset(this->cur_row, 0, this->columns + 1);
getNext()->finish();
}