mirror of https://github.com/qpdf/qpdf.git
147 lines
2.6 KiB
C++
147 lines
2.6 KiB
C++
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#include <qpdf/Pl_PNGFilter.hh>
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#include <string.h>
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Pl_PNGFilter::Pl_PNGFilter(char const* identifier, Pipeline* next,
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action_e action, unsigned int columns,
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unsigned int bytes_per_pixel) :
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Pipeline(identifier, next),
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action(action),
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columns(columns),
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cur_row(0),
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prev_row(0),
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buf1(0),
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buf2(0),
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pos(0)
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{
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this->buf1 = new unsigned char[columns + 1];
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this->buf2 = new unsigned char[columns + 1];
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this->cur_row = buf1;
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// number of bytes per incoming row
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this->incoming = (action == a_encode ? columns : columns + 1);
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}
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Pl_PNGFilter::~Pl_PNGFilter()
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{
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delete [] buf1;
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delete [] buf2;
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}
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void
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Pl_PNGFilter::write(unsigned char* data, int len)
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{
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int left = this->incoming - this->pos;
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unsigned int offset = 0;
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while (len >= left)
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{
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// finish off current row
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memcpy(this->cur_row + this->pos, data + offset, left);
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offset += left;
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len -= left;
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processRow();
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// Swap rows
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unsigned char* t = this->prev_row;
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this->prev_row = this->cur_row;
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this->cur_row = t ? t : this->buf2;
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memset(this->cur_row, 0, this->columns + 1);
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left = this->incoming;
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this->pos = 0;
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}
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if (len)
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{
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memcpy(this->cur_row + this->pos, data + offset, len);
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}
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this->pos += len;
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}
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void
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Pl_PNGFilter::processRow()
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{
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if (this->action == a_encode)
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{
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encodeRow();
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}
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else
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{
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decodeRow();
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}
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}
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void
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Pl_PNGFilter::decodeRow()
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{
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int filter = (int) this->cur_row[0];
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if (this->prev_row)
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{
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switch (filter)
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{
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case 0: // none
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break;
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case 1: // sub
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throw Exception("sub filter not implemented");
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break;
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case 2: // up
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for (unsigned int i = 1; i <= this->columns; ++i)
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{
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this->cur_row[i] += this->prev_row[i];
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}
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break;
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case 3: // average
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throw Exception("average filter not implemented");
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break;
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case 4: // Paeth
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throw Exception("Paeth filter not implemented");
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break;
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default:
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// ignore
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break;
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}
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}
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getNext()->write(this->cur_row + 1, this->columns);
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}
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void
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Pl_PNGFilter::encodeRow()
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{
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// For now, hard-code to using UP filter.
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unsigned char ch = 2;
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getNext()->write(&ch, 1);
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if (this->prev_row)
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{
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for (unsigned int i = 0; i < this->columns; ++i)
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{
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ch = this->cur_row[i] - this->prev_row[i];
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getNext()->write(&ch, 1);
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}
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}
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else
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{
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getNext()->write(this->cur_row, this->columns);
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}
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}
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void
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Pl_PNGFilter::finish()
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{
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if (this->pos)
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{
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// write partial row
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processRow();
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}
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this->prev_row = 0;
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this->cur_row = buf1;
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this->pos = 0;
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memset(this->cur_row, 0, this->columns + 1);
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getNext()->finish();
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}
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