External Lib read from QBuffer on Calback problem

[patrik08]

I read compressed image from libpng .. my EncoderWriteCallback write is ok and running
but the read (EncoderReadCallback) is not ok why?

is the same 1:1 QByteArray wo libpng has writteln ... why now it can not read?
the QByteArray is not from qpixmap or qimage.

on debug qbuffer is readable and having size ..


I start the callback so...

png_ptr_read = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if(png_ptr_read == NULL)  {
        qWarning("unable to create read struct");
        return;
    }
    info_ptr_read = png_create_info_struct(png_ptr_read);
    if(info_ptr_read == NULL) {
        qWarning("unable to create info struct");
        return;
    }
    png_set_sig_bytes(png_ptr_read, 8);
    APNGImageStream myqtchunk(0,frame.stream());   /* stream() = QByteArray */
    png_set_read_fn(png_ptr_read,&myqtchunk,EncoderReadCallback);

png_ptr_read = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if(png_ptr_read == NULL)  {
        qWarning("unable to create read struct");
        return;
    }
    info_ptr_read = png_create_info_struct(png_ptr_read);
    if(info_ptr_read == NULL) {
        qWarning("unable to create info struct");
        return;
    }
    png_set_sig_bytes(png_ptr_read, 8);
    APNGImageStream myqtchunk(0,frame.stream());   /* stream() = QByteArray */
    png_set_read_fn(png_ptr_read,&myqtchunk,EncoderReadCallback);

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and this is reader and writer

#define PNG_USER_MEM_SUPPORTED
#define PNG_WRITE_bKGD_SUPPORTED
 
 
////base ref http://www.littlesvr.ca/apng/tutorial/x148.html
/* png lib from firefox 3 is patch  to APNG format! */
#include "../moz_png/png.h"
 
/* device to write or read image frames */
class APNGImageStream {
  public:
  APNGImageStream( const int mode , QByteArray in = QByteArray() ) 
  :dev(new QBuffer()),bytes(in) 
  {
   dev->setBuffer(&bytes);
   if (mode == 1) {
    dev->open(QIODevice::WriteOnly);
   } else {
    dev->open(QIODevice::ReadOnly);
   }
  }
  ~APNGImageStream()
  {
   dev->close();
  }
  QBuffer *device() { return dev; }
  bool isValid() { return img.loadFromData(dev->data()); }
  QByteArray stream() { return dev->data(); }
  QImage img;
  QBuffer *dev;
  QByteArray bytes;
};
 
// Called by libpng to flush its internal buffer to ours.
static void EncoderWriteCallback(png_structp png, png_bytep data,
                                 png_size_t size) {
  APNGImageStream *state = static_cast<APNGImageStream*>(png_get_io_ptr(png));
  Q_ASSERT(state->device());
  state->device()->write((char*)data,size);
}
 
// Called by libpng to read original QByteArray that has self created .
static void EncoderReadCallback(png_structp png, png_bytep data, 
                                 png_size_t sizer)  {
    APNGImageStream *state = static_cast<APNGImageStream*>(png_get_io_ptr(png));
    Q_ASSERT(state->device());
    qDebug() << "### size to read 1/0  " << state->stream().size() << "," << state->device()->isReadable();
    state->device()->read((char*)data,sizer);
    qDebug() << "### read callback length   " << sizer; 
}

#define PNG_USER_MEM_SUPPORTED
#define PNG_WRITE_bKGD_SUPPORTED


////base ref http://www.littlesvr.ca/apng/tutorial/x148.html
/* png lib from firefox 3 is patch  to APNG format! */
#include "../moz_png/png.h"

/* device to write or read image frames */
class APNGImageStream {
  public:
  APNGImageStream( const int mode , QByteArray in = QByteArray() ) 
  :dev(new QBuffer()),bytes(in) 
  {
   dev->setBuffer(&bytes);
   if (mode == 1) {
    dev->open(QIODevice::WriteOnly);
   } else {
    dev->open(QIODevice::ReadOnly);
   }
  }
  ~APNGImageStream()
  {
   dev->close();
  }
  QBuffer *device() { return dev; }
  bool isValid() { return img.loadFromData(dev->data()); }
  QByteArray stream() { return dev->data(); }
  QImage img;
  QBuffer *dev;
  QByteArray bytes;
};

// Called by libpng to flush its internal buffer to ours.
static void EncoderWriteCallback(png_structp png, png_bytep data,
                                 png_size_t size) {
  APNGImageStream *state = static_cast<APNGImageStream*>(png_get_io_ptr(png));
  Q_ASSERT(state->device());
  state->device()->write((char*)data,size);
}

// Called by libpng to read original QByteArray that has self created .
static void EncoderReadCallback(png_structp png, png_bytep data, 
                                 png_size_t sizer)  {
    APNGImageStream *state = static_cast<APNGImageStream*>(png_get_io_ptr(png));
    Q_ASSERT(state->device());
    qDebug() << "### size to read 1/0  " << state->stream().size() << "," << state->device()->isReadable();
    state->device()->read((char*)data,sizer);
    qDebug() << "### read callback length   " << sizer; 
}

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[patrik08]

i try to write on device and i leave dev->setBuffer(&bytes);
is the same, libpng can only write on device .. why not read ..

qt access the image isValid on read & write ....

i can not set file over 100 png frame movie....

public:
  APNGImageStream( const int mode , QByteArray in = QByteArray() ) 
  :dev(new QBuffer()),bytes(in) 
  {
   if (mode == 1) {
     /* pnglib write in */
     dev->setBuffer(&bytes);
     dev->open(QIODevice::WriteOnly);
   } else {
     /* qt write in && png read out */
     dev->open(QIODevice::ReadWrite);
     dev->write(bytes);
     dev->seek(0);
   }
  }

public:
  APNGImageStream( const int mode , QByteArray in = QByteArray() ) 
  :dev(new QBuffer()),bytes(in) 
  {
   if (mode == 1) {
     /* pnglib write in */
     dev->setBuffer(&bytes);
     dev->open(QIODevice::WriteOnly);
   } else {
     /* qt write in && png read out */
     dev->open(QIODevice::ReadWrite);
     dev->write(bytes);
     dev->seek(0);
   }
  }

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[patrik08]

I have resolved the big QBuffer problem
only writeBlock && readBlock and all external lib ... in this case libpng can write or read like a virtual file... && class PngEventBuffer : public QEvent the post event can paint a progress dialog by read or write....

QEvent inside a CallBack function .. this is new tecnology...

class APNGwrittelStream {
  public:
  APNGwrittelStream(QObject *o) :d(new QBuffer()),creator(o)
  {
  d->open(QIODevice::ReadWrite);
  start();
  }
  ~APNGwrittelStream()
  {
   d->close();
  }
  void start() { d->seek(0); }
  QBuffer *device() { return d; }
  bool isValid() { return img.loadFromData(stream()); }
  QByteArray stream() { return d->data(); }
  QImage img;
  QBuffer *d;
  QObject *creator;
}; 
 
 
/* read and write progress  */
class PngEventBuffer : public QEvent
{
	//QEvent::User==1000
 
public:
    PngEventBuffer(int status, int total )
	: QEvent( QEvent::User ),s(status),t(total)
    {  }
 int pos() const { return s; }
 int sum() const { return t; }
 
private:
    int s;
    int t;
};
 
 
// Called by libpng to flush its internal buffer to ours.
static void EncoderWriteCallback(png_structp png, png_bytep data,
                                 png_size_t size) {
  APNGwrittelStream *state = static_cast<APNGwrittelStream*>(png_get_io_ptr(png));
  Q_ASSERT(state->device());
  state->device()->writeBlock((char*)data,size);                              
  ///////qDebug() << "### pos  ->" << state->device()->pos();
  qApp->postEvent(state->creator,new PngEventBuffer(state->device()->pos(),
                                   0));
 
}
 
// Called by libpng to read QImage on buffer .
static void EncoderReaderCallback(png_structp png, png_bytep data, 
                                   png_size_t size)
{
  APNGwrittelStream *state = static_cast<APNGwrittelStream*>(png_get_io_ptr(png));
  Q_ASSERT(state->device());
  state->device()->readBlock((char*)data,size);                              
  /////////qDebug() << "### pos  ->" << state->device()->pos();
  qApp->postEvent(state->creator,new PngEventBuffer(state->device()->pos(),
                                   state->device()->bytesAvailable()));
}

class APNGwrittelStream {
  public:
  APNGwrittelStream(QObject *o) :d(new QBuffer()),creator(o)
  {
  d->open(QIODevice::ReadWrite);
  start();
  }
  ~APNGwrittelStream()
  {
   d->close();
  }
  void start() { d->seek(0); }
  QBuffer *device() { return d; }
  bool isValid() { return img.loadFromData(stream()); }
  QByteArray stream() { return d->data(); }
  QImage img;
  QBuffer *d;
  QObject *creator;
}; 


/* read and write progress  */
class PngEventBuffer : public QEvent
{
	//QEvent::User==1000
    
public:
    PngEventBuffer(int status, int total )
	: QEvent( QEvent::User ),s(status),t(total)
    {  }
 int pos() const { return s; }
 int sum() const { return t; }

private:
    int s;
    int t;
};


// Called by libpng to flush its internal buffer to ours.
static void EncoderWriteCallback(png_structp png, png_bytep data,
                                 png_size_t size) {
  APNGwrittelStream *state = static_cast<APNGwrittelStream*>(png_get_io_ptr(png));
  Q_ASSERT(state->device());
  state->device()->writeBlock((char*)data,size);                              
  ///////qDebug() << "### pos  ->" << state->device()->pos();
  qApp->postEvent(state->creator,new PngEventBuffer(state->device()->pos(),
                                   0));

}

// Called by libpng to read QImage on buffer .
static void EncoderReaderCallback(png_structp png, png_bytep data, 
                                   png_size_t size)
{
  APNGwrittelStream *state = static_cast<APNGwrittelStream*>(png_get_io_ptr(png));
  Q_ASSERT(state->device());
  state->device()->readBlock((char*)data,size);                              
  /////////qDebug() << "### pos  ->" << state->device()->pos();
  qApp->postEvent(state->creator,new PngEventBuffer(state->device()->pos(),
                                   state->device()->bytesAvailable()));
}

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