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Thread: Retrieve QByteArray in .png from SQL database

  1. #1
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    Post Retrieve QByteArray in .png from SQL database

    hello

    I have stored image in arraybyte in database and I am also able to run a query to retrieve arraybyte in QPixmap and displaying on QLable.

    I want to retrieve the same arraybyte from database but this time I have to store that file in automatic generated folder (Any name) with the format of PNG.

    What classes I can use to generate folder for storing my image file ?

    How to save the QPixmap in any folder or directory ?
    Qt Code:
    1. QPixmap::save()
    To copy to clipboard, switch view to plain text mode 
    just gives boolean value...but does it save file in a specific location?

    Looking for your guidance..

    Thanks in advance...

  2. #2
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    Default Re: Retrieve QByteArray in .png from SQL database

    Simply use correct variant of method QPixmap::save.

  3. #3
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    Default Re: Retrieve QByteArray in .png from SQL database

    Which format do you get the date in when you query the database?

    If it is PNG already you could just write the data directly into a file.

    If you need to decode it first, e.g. if it is saved in a different format in the database, then use QImage for loading/saving if you don't need to display it.
    (saves two conversions between QImage and QPixmap)

    Cheers,
    _

  4. #4
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    Post Re: Retrieve QByteArray in .png from SQL database

    my image data is in bytes only. I am trying to save byte data using QPixmap::save in specific directory but I am not getting any png file in that specific folder.


    Added after 8 minutes:


    code for saving byte image in specific folder.
    Qt Code:
    1. QPixmap pix ("C:/Folder");
    2. QByteArray bytes = dataFromDatabase; //It is a byteArray data
    3. QBuffer buf(&bytes);
    4. buf.open(QIODevice::WriteOnly);
    5. pix.save(&buf, "PNG");
    To copy to clipboard, switch view to plain text mode 

    I used this code to save png file in folder but after running this code I am not getting any file in that folder.
    Last edited by sam123; 12th July 2016 at 10:47.

  5. #5
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    Default Re: Retrieve QByteArray in .png from SQL database

    Quote Originally Posted by sam123 View Post
    my image data is in bytes only
    You mean like 32-bit ARGB or similar?

    Quote Originally Posted by sam123 View Post
    I used this code to save png file in folder but after running this code I am not getting any file in that folder.
    If you want to save to a png file, why do you write into the buffer?

    Cheers,
    _

  6. #6
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    Default Re: Retrieve QByteArray in .png from SQL database

    yes its similar, what would be the correct method to save png in specific folder. Could you please suggest me.

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    Default Re: Retrieve QByteArray in .png from SQL database

    Either use QFile instead of the buffer or just use the save() overload that takes a filename.

    Cheers,
    _

    P.S.: as I said before, if you don't need to display the image use QImage instead of forcing two QImage<->QPixmap conversions

  8. #8
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    Default Re: Retrieve QByteArray in .png from SQL database

    From line 1 of code : You try to work with QPixmap from file Folder in main directory of disk C:. Is this what You want ? I don't think so.

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