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Thread: Save images to database

  1. #1
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    Default Save images to database

    QT4 windows

    I would like to save an image file (jpg,bmp...) into an sqlite database as a BLOB. What format must it be in to save it to the database? I can't find anything that converts into a ByteArray.

    Once that problem is solved I will then have to view the image form the database. So whatever format i save it in I will have to be able to put it back into QImage or QPixmap.

    Thanks.

  2. #2
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    Default Re: Save images to database

    If you want Qt to decode and/or encode it, the format should be on this list.
    If you just need the data from an image file, QFile::readAll() should be enough. If you want to encode the image in memory, you need the following:

    Qt Code:
    1. QBuffer buffer;
    2. QImageWriter writer(&buffer, "PNG");
    3. writer.write(image);
    4. QByteArray data = buffer.data();
    To copy to clipboard, switch view to plain text mode 

    To decode:

    Qt Code:
    1. QByteArray array = variant.toByteArray();
    2. QBuffer buffer(&array);
    3. QImageReader reader(&buffer, "PNG");
    4. QImage image = reader.read();
    To copy to clipboard, switch view to plain text mode 

    I'm assuming you know how to insert the QByteArray into the database and get it out, but If you any clarification, just ask.
    Last edited by init2null; 5th May 2006 at 02:56.
    ImageRocket - My Qt4-based image editing program
    Project Page / Screenshots / Source

  3. The following user says thank you to init2null for this useful post:

    jnk5y (5th May 2006)

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    Default Re: Save images to database

    It should be possible to convert between QVariant and QImage with a single line of code.
    Last edited by jacek; 5th May 2006 at 20:28. Reason: fixed typo

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    Default Re: Save images to database

    Thanks init2null. I actually did it a similar way. I used QFile::readAll() and stored that into the database. Then used QImage::loadFromData() to put into memory.

    Now I want to view it and I want to display it with a few lineEdits and a couple of buttons in a QMainWindow. Unfortunately the widget I want to display it on is not giving me back it's proper size in order to scale the image. Do you know why it would do that?

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    Default Re: Save images to database

    Quote Originally Posted by jnk5y
    Thanks init2null. I actually did it a similar way. I used QFile::readAll() and stored that into the database. Then used QImage::loadFromData() to put into memory.

    Now I want to view it and I want to display it with a few lineEdits and a couple of buttons in a QMainWindow. Unfortunately the widget I want to display it on is not giving me back it's proper size in order to scale the image. Do you know why it would do that?
    Widgets do not always correctly report their sizes until just before they are shown (particularly when they are used in layouts). Defer your code until the showEvent() to get accurate widget sizes.
    Save yourself some pain. Learn C++ before learning Qt.

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