diff --git a/src/imageformats/rgb.cpp b/src/imageformats/rgb.cpp
index 2eb60a8..432def8 100644
--- a/src/imageformats/rgb.cpp
+++ b/src/imageformats/rgb.cpp
@@ -1,746 +1,746 @@
 // kimgio module for SGI images
 //
 // Copyright (C) 2004  Melchior FRANZ  <mfranz@kde.org>
 //
 // This program is free software; you can redistribute it and/or
 // modify it under the terms of the Lesser GNU General Public License as
 // published by the Free Software Foundation; either version 2 of the
 // License, or (at your option) any later version.
 
 /* this code supports:
  * reading:
  *     everything, except images with 1 dimension or images with
  *     mapmode != NORMAL (e.g. dithered); Images with 16 bit
  *     precision or more than 4 layers are stripped down.
  * writing:
  *     Run Length Encoded (RLE) or Verbatim (uncompressed)
  *     (whichever is smaller)
  *
  * Please report if you come across rgb/rgba/sgi/bw files that aren't
  * recognized. Also report applications that can't deal with images
  * saved by this filter.
  */
 
 #include "rgb_p.h"
 
 #include <QMap>
 #include <QVector>
 
 #include <QImage>
 #include <QDebug>
 
 class RLEData : public QVector<uchar>
 {
 public:
     RLEData() {}
     RLEData(const uchar *d, uint l, uint o) : _offset(o)
     {
         for (uint i = 0; i < l; i++) {
             append(d[i]);
         }
     }
     bool operator<(const RLEData &) const;
     void write(QDataStream &s);
     uint offset() const
     {
         return _offset;
     }
 
 private:
     uint _offset;
 };
 
 class RLEMap : public QMap<RLEData, uint>
 {
 public:
     RLEMap() : _counter(0), _offset(0) {}
     uint insert(const uchar *d, uint l);
     QVector<const RLEData *> vector();
     void setBaseOffset(uint o)
     {
         _offset = o;
     }
 
 private:
     uint _counter;
     uint _offset;
 };
 
 class SGIImage
 {
 public:
     SGIImage(QIODevice *device);
     ~SGIImage();
 
     bool readImage(QImage &);
     bool writeImage(const QImage &);
 
 private:
     enum { NORMAL, DITHERED, SCREEN, COLORMAP }; // colormap
     QIODevice *_dev;
     QDataStream _stream;
 
     quint8 _rle;
     quint8 _bpc;
     quint16 _dim;
     quint16 _xsize;
     quint16 _ysize;
     quint16 _zsize;
     quint32 _pixmin;
     quint32 _pixmax;
     char _imagename[80];
     quint32 _colormap;
 
     quint32 *_starttab;
     quint32 *_lengthtab;
     QByteArray _data;
     QByteArray::Iterator _pos;
     RLEMap _rlemap;
     QVector<const RLEData *> _rlevector;
     uint _numrows;
 
     bool readData(QImage &);
     bool getRow(uchar *dest);
 
     void writeHeader();
     void writeRle();
     void writeVerbatim(const QImage &);
     bool scanData(const QImage &);
     uint compact(uchar *, uchar *);
     uchar intensity(uchar);
 };
 
 SGIImage::SGIImage(QIODevice *io) :
     _starttab(nullptr),
     _lengthtab(nullptr)
 {
     _dev = io;
     _stream.setDevice(_dev);
 }
 
 SGIImage::~SGIImage()
 {
     delete[] _starttab;
     delete[] _lengthtab;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 bool SGIImage::getRow(uchar *dest)
 {
     int n, i;
     if (!_rle) {
         for (i = 0; i < _xsize; i++) {
             if (_pos >= _data.end()) {
                 return false;
             }
             dest[i] = uchar(*_pos);
             _pos += _bpc;
         }
         return true;
     }
 
     for (i = 0; i < _xsize;) {
         if (_bpc == 2) {
             _pos++;
         }
         if (_pos >= _data.end()) {
             return false;
         }
         n = *_pos & 0x7f;
         if (!n) {
             break;
         }
 
         if (*_pos++ & 0x80) {
             for (; i < _xsize && _pos < _data.end() && n--; i++) {
                 *dest++ = *_pos;
                 _pos += _bpc;
             }
         } else {
             for (; i < _xsize && n--; i++) {
                 *dest++ = *_pos;
             }
 
             _pos += _bpc;
         }
     }
     return i == _xsize;
 }
 
 bool SGIImage::readData(QImage &img)
 {
     QRgb *c;
     quint32 *start = _starttab;
     QByteArray lguard(_xsize, 0);
     uchar *line = (uchar *)lguard.data();
     unsigned x, y;
 
     if (!_rle) {
         _pos = _data.begin();
     }
 
     for (y = 0; y < _ysize; y++) {
         if (_rle) {
             _pos = _data.begin() + *start++;
         }
         if (!getRow(line)) {
             return false;
         }
         c = (QRgb *)img.scanLine(_ysize - y - 1);
         for (x = 0; x < _xsize; x++, c++) {
             *c = qRgb(line[x], line[x], line[x]);
         }
     }
 
     if (_zsize == 1) {
         return true;
     }
 
     if (_zsize != 2) {
         for (y = 0; y < _ysize; y++) {
             if (_rle) {
                 _pos = _data.begin() + *start++;
             }
             if (!getRow(line)) {
                 return false;
             }
             c = (QRgb *)img.scanLine(_ysize - y - 1);
             for (x = 0; x < _xsize; x++, c++) {
                 *c = qRgb(qRed(*c), line[x], line[x]);
             }
         }
 
         for (y = 0; y < _ysize; y++) {
             if (_rle) {
                 _pos = _data.begin() + *start++;
             }
             if (!getRow(line)) {
                 return false;
             }
             c = (QRgb *)img.scanLine(_ysize - y - 1);
             for (x = 0; x < _xsize; x++, c++) {
                 *c = qRgb(qRed(*c), qGreen(*c), line[x]);
             }
         }
 
         if (_zsize == 3) {
             return true;
         }
     }
 
     for (y = 0; y < _ysize; y++) {
         if (_rle) {
             _pos = _data.begin() + *start++;
         }
         if (!getRow(line)) {
             return false;
         }
         c = (QRgb *)img.scanLine(_ysize - y - 1);
         for (x = 0; x < _xsize; x++, c++) {
             *c = qRgba(qRed(*c), qGreen(*c), qBlue(*c), line[x]);
         }
     }
 
     return true;
 }
 
 bool SGIImage::readImage(QImage &img)
 {
     qint8 u8;
     qint16 u16;
     qint32 u32;
 
 //     qDebug() << "reading rgb ";
 
     // magic
     _stream >> u16;
     if (u16 != 0x01da) {
         return false;
     }
 
     // verbatim/rle
     _stream >> _rle;
 //     qDebug() << (_rle ? "RLE" : "verbatim");
     if (_rle > 1) {
         return false;
     }
 
     // bytes per channel
     _stream >> _bpc;
 //     qDebug() << "bytes per channel: " << int(_bpc);
     if (_bpc == 1)
         ;
     else if (_bpc == 2) {
 //         qDebug() << "dropping least significant byte";
     } else {
         return false;
     }
 
     // number of dimensions
     _stream >> _dim;
 //     qDebug() << "dimensions: " << _dim;
     if (_dim < 1 || _dim > 3) {
         return false;
     }
 
     _stream >> _xsize >> _ysize >> _zsize >> _pixmin >> _pixmax >> u32;
 //     qDebug() << "x: " << _xsize;
 //     qDebug() << "y: " << _ysize;
 //     qDebug() << "z: " << _zsize;
 
     // name
     _stream.readRawData(_imagename, 80);
     _imagename[79] = '\0';
 
     _stream >> _colormap;
 //     qDebug() << "colormap: " << _colormap;
     if (_colormap != NORMAL) {
         return false;    // only NORMAL supported
     }
 
     for (int i = 0; i < 404; i++) {
         _stream >> u8;
     }
 
     if (_dim == 1) {
 //         qDebug() << "1-dimensional images aren't supported yet";
         return false;
     }
 
     if (_stream.atEnd()) {
         return false;
     }
 
     img = QImage(_xsize, _ysize, QImage::Format_RGB32);
 
     if (_zsize == 0 )
         return false;
 
     if (_zsize == 2 || _zsize == 4) {
         img = img.convertToFormat(QImage::Format_ARGB32);
     } else if (_zsize > 4) {
 //         qDebug() << "using first 4 of " << _zsize << " channels";
         // Only let this continue if it won't cause a int overflow later
         // this is most likely a broken file anyway
         if (_ysize > std::numeric_limits<int>::max() / _zsize)
             return false;
     }
 
     _numrows = _ysize * _zsize;
 
     if (_rle) {
         uint l;
         _starttab = new quint32[_numrows];
         for (l = 0; !_stream.atEnd() && l < _numrows; l++) {
             _stream >> _starttab[l];
             _starttab[l] -= 512 + _numrows * 2 * sizeof(quint32);
         }
 
         _lengthtab = new quint32[_numrows];
         for (l = 0; l < _numrows; l++) {
             _stream >> _lengthtab[l];
         }
     }
 
     _data = _dev->readAll();
 
     // sanity check
     if (_rle)
         for (uint o = 0; o < _numrows; o++)
             // don't change to greater-or-equal!
             if (_starttab[o] + _lengthtab[o] > (uint)_data.size()) {
 //                 qDebug() << "image corrupt (sanity check failed)";
                 return false;
             }
 
     if (!readData(img)) {
 //         qDebug() << "image corrupt (incomplete scanline)";
         return false;
     }
 
     return true;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 void RLEData::write(QDataStream &s)
 {
     for (int i = 0; i < size(); i++) {
         s << at(i);
     }
 }
 
 bool RLEData::operator<(const RLEData &b) const
 {
     uchar ac, bc;
     for (int i = 0; i < qMin(size(), b.size()); i++) {
         ac = at(i);
         bc = b[i];
         if (ac != bc) {
             return ac < bc;
         }
     }
     return size() < b.size();
 }
 
 uint RLEMap::insert(const uchar *d, uint l)
 {
     RLEData data = RLEData(d, l, _offset);
     Iterator it = find(data);
     if (it != end()) {
         return it.value();
     }
 
     _offset += l;
     return QMap<RLEData, uint>::insert(data, _counter++).value();
 }
 
 QVector<const RLEData *> RLEMap::vector()
 {
     QVector<const RLEData *> v(size());
     for (Iterator it = begin(); it != end(); ++it) {
         v.replace(it.value(), &it.key());
     }
 
     return v;
 }
 
 uchar SGIImage::intensity(uchar c)
 {
     if (c < _pixmin) {
         _pixmin = c;
     }
     if (c > _pixmax) {
         _pixmax = c;
     }
     return c;
 }
 
 uint SGIImage::compact(uchar *d, uchar *s)
 {
     uchar *dest = d, *src = s, patt, *t, *end = s + _xsize;
     int i, n;
     while (src < end) {
         for (n = 0, t = src; t + 2 < end && !(*t == t[1] && *t == t[2]); t++) {
             n++;
         }
 
         while (n) {
             i = n > 126 ? 126 : n;
             n -= i;
             *dest++ = 0x80 | i;
             while (i--) {
                 *dest++ = *src++;
             }
         }
 
         if (src == end) {
             break;
         }
 
         patt = *src++;
         for (n = 1; src < end && *src == patt; src++) {
             n++;
         }
 
         while (n) {
             i = n > 126 ? 126 : n;
             n -= i;
             *dest++ = i;
             *dest++ = patt;
         }
     }
     *dest++ = 0;
     return dest - d;
 }
 
 bool SGIImage::scanData(const QImage &img)
 {
     quint32 *start = _starttab;
     QByteArray lineguard(_xsize * 2, 0);
     QByteArray bufguard(_xsize, 0);
     uchar *line = (uchar *)lineguard.data();
     uchar *buf = (uchar *)bufguard.data();
     const QRgb *c;
     unsigned x, y;
     uint len;
 
     for (y = 0; y < _ysize; y++) {
         c = reinterpret_cast<const QRgb *>(img.scanLine(_ysize - y - 1));
         for (x = 0; x < _xsize; x++) {
             buf[x] = intensity(qRed(*c++));
         }
         len = compact(line, buf);
         *start++ = _rlemap.insert(line, len);
     }
 
     if (_zsize == 1) {
         return true;
     }
 
     if (_zsize != 2) {
         for (y = 0; y < _ysize; y++) {
             c = reinterpret_cast<const QRgb *>(img.scanLine(_ysize - y - 1));
             for (x = 0; x < _xsize; x++) {
                 buf[x] = intensity(qGreen(*c++));
             }
             len = compact(line, buf);
             *start++ = _rlemap.insert(line, len);
         }
 
         for (y = 0; y < _ysize; y++) {
             c = reinterpret_cast<const QRgb *>(img.scanLine(_ysize - y - 1));
             for (x = 0; x < _xsize; x++) {
                 buf[x] = intensity(qBlue(*c++));
             }
             len = compact(line, buf);
             *start++ = _rlemap.insert(line, len);
         }
 
         if (_zsize == 3) {
             return true;
         }
     }
 
     for (y = 0; y < _ysize; y++) {
         c = reinterpret_cast<const QRgb *>(img.scanLine(_ysize - y - 1));
         for (x = 0; x < _xsize; x++) {
             buf[x] = intensity(qAlpha(*c++));
         }
         len = compact(line, buf);
         *start++ = _rlemap.insert(line, len);
     }
 
     return true;
 }
 
 void SGIImage::writeHeader()
 {
     _stream << quint16(0x01da);
     _stream << _rle << _bpc << _dim;
     _stream << _xsize << _ysize << _zsize;
     _stream << _pixmin << _pixmax;
     _stream << quint32(0);
 
     for (int i = 0; i < 80; i++) {
         _imagename[i] = '\0';
     }
     _stream.writeRawData(_imagename, 80);
 
     _stream << _colormap;
     for (int i = 0; i < 404; i++) {
         _stream << quint8(0);
     }
 }
 
 void SGIImage::writeRle()
 {
     _rle = 1;
 //     qDebug() << "writing RLE data";
     writeHeader();
     uint i;
 
     // write start table
     for (i = 0; i < _numrows; i++) {
         _stream << quint32(_rlevector[_starttab[i]]->offset());
     }
 
     // write length table
     for (i = 0; i < _numrows; i++) {
         _stream << quint32(_rlevector[_starttab[i]]->size());
     }
 
     // write data
     for (i = 0; (int)i < _rlevector.size(); i++) {
         const_cast<RLEData *>(_rlevector[i])->write(_stream);
     }
 }
 
 void SGIImage::writeVerbatim(const QImage &img)
 {
     _rle = 0;
 //     qDebug() << "writing verbatim data";
     writeHeader();
 
     const QRgb *c;
     unsigned x, y;
 
     for (y = 0; y < _ysize; y++) {
         c = reinterpret_cast<const QRgb *>(img.scanLine(_ysize - y - 1));
         for (x = 0; x < _xsize; x++) {
             _stream << quint8(qRed(*c++));
         }
     }
 
     if (_zsize == 1) {
         return;
     }
 
     if (_zsize != 2) {
         for (y = 0; y < _ysize; y++) {
             c = reinterpret_cast<const QRgb *>(img.scanLine(_ysize - y - 1));
             for (x = 0; x < _xsize; x++) {
                 _stream << quint8(qGreen(*c++));
             }
         }
 
         for (y = 0; y < _ysize; y++) {
             c = reinterpret_cast<const QRgb *>(img.scanLine(_ysize - y - 1));
             for (x = 0; x < _xsize; x++) {
                 _stream << quint8(qBlue(*c++));
             }
         }
 
         if (_zsize == 3) {
             return;
         }
     }
 
     for (y = 0; y < _ysize; y++) {
         c = reinterpret_cast<const QRgb *>(img.scanLine(_ysize - y - 1));
         for (x = 0; x < _xsize; x++) {
             _stream << quint8(qAlpha(*c++));
         }
     }
 }
 
 bool SGIImage::writeImage(const QImage &image)
 {
 //     qDebug() << "writing "; // TODO add filename
     QImage img = image;
     if (img.allGray()) {
         _dim = 2, _zsize = 1;
     } else {
         _dim = 3, _zsize = 3;
     }
 
     if (img.format() == QImage::Format_ARGB32) {
         _dim = 3, _zsize++;
     }
 
     img = img.convertToFormat(QImage::Format_RGB32);
     if (img.isNull()) {
 //         qDebug() << "can't convert image to depth 32";
         return false;
     }
 
     _bpc = 1;
     _xsize = img.width();
     _ysize = img.height();
     _pixmin = ~0u;
     _pixmax = 0;
     _colormap = NORMAL;
     _numrows = _ysize * _zsize;
     _starttab = new quint32[_numrows];
     _rlemap.setBaseOffset(512 + _numrows * 2 * sizeof(quint32));
 
     if (!scanData(img)) {
 //         qDebug() << "this can't happen";
         return false;
     }
 
     _rlevector = _rlemap.vector();
 
     long verbatim_size = _numrows * _xsize;
     long rle_size = _numrows * 2 * sizeof(quint32);
     for (int i = 0; i < _rlevector.size(); i++) {
         rle_size += _rlevector[i]->size();
     }
 
 //     qDebug() << "minimum intensity: " << _pixmin;
 //     qDebug() << "maximum intensity: " << _pixmax;
 //     qDebug() << "saved scanlines: " << _numrows - _rlemap.size();
 //     qDebug() << "total savings: " << (verbatim_size - rle_size) << " bytes";
 //     qDebug() << "compression: " << (rle_size * 100.0 / verbatim_size) << '%';
 
     if (verbatim_size <= rle_size) {
         writeVerbatim(img);
     } else {
         writeRle();
     }
     return true;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 RGBHandler::RGBHandler()
 {
 }
 
 bool RGBHandler::canRead() const
 {
     if (canRead(device())) {
         setFormat("rgb");
         return true;
     }
     return false;
 }
 
 bool RGBHandler::read(QImage *outImage)
 {
     SGIImage sgi(device());
     return sgi.readImage(*outImage);
 }
 
 bool RGBHandler::write(const QImage &image)
 {
     SGIImage sgi(device());
     return sgi.writeImage(image);
 }
 
 bool RGBHandler::canRead(QIODevice *device)
 {
     if (!device) {
         qWarning("RGBHandler::canRead() called with no device");
         return false;
     }
 
     const qint64 oldPos = device->pos();
     const QByteArray head = device->readLine(64);
     int readBytes = head.size();
 
     if (device->isSequential()) {
         while (readBytes > 0) {
             device->ungetChar(head[readBytes-- - 1]);
         }
 
     } else {
         device->seek(oldPos);
     }
 
-    return head.size() >= 4 && head.startsWith("\x01\xda\x01") && (head[3] == 1 || head[3] == 2);
+    return head.size() >= 4 && head.startsWith("\x01\xda") && (head[2] == 0 || head[2] == 1) && (head[3] == 1 || head[3] == 2);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 QImageIOPlugin::Capabilities RGBPlugin::capabilities(QIODevice *device, const QByteArray &format) const
 {
     if (format == "rgb" || format ==  "rgba" ||
             format ==  "bw" || format == "sgi") {
         return Capabilities(CanRead | CanWrite);
     }
     if (!format.isEmpty()) {
         return {};
     }
     if (!device->isOpen()) {
         return {};
     }
 
     Capabilities cap;
     if (device->isReadable() && RGBHandler::canRead(device)) {
         cap |= CanRead;
     }
     if (device->isWritable()) {
         cap |= CanWrite;
     }
     return cap;
 }
 
 QImageIOHandler *RGBPlugin::create(QIODevice *device, const QByteArray &format) const
 {
     QImageIOHandler *handler = new RGBHandler;
     handler->setDevice(device);
     handler->setFormat(format);
     return handler;
 }