what is the best way to create a QPixmap image from raw data?

c.savur

I have raw image data that need to be converted into QPixmap. The way I am doing is below,

QPixmap convert2Pixmap(int w, int h, string colorSpace, std::vector<unsigned char> buffer)
{
    // create an image
    QImage img( &buffer.front(), w, h, w*getBytePerLine(colorSpace), getImageFormat(colorSpace) );
    return QPixmap::fromImage(img);
}

right now it takes about 50-60 ms to convert RGB 24 bit image with 4608x2400. However, I want to speed up this process. Is there any better way to do this?

Thank you in advance.

mrjj

Hi
You are already use the smart QImage constructor that dont copy data
and I assume both getBytePerLine and getImageFormat are cheap.

You seems to send the buffer as copy ?
.. std::vector<unsigned char> buffer)
I would expect
..std::vector<unsigned char> & buffer)

Or do i read it wrong ?

c.savur

@mrjj said:

Hi
You are already use the smart QImage constructor that dont copy data
and I assume both getBytePerLine and getImageFormat are cheap.

Yes, they are. They just return corresponding value based on color format.

You seems to send the buffer as copy ?
.. std::vector<unsigned char> buffer)
I would expect
..std::vector<unsigned char> & buffer)

Or do i read it wrong ?

You are right, how did I miss that part. After changing to reference it improved by ~20 ms.

Thank you.

mrjj

Super
that was a nice reduction :)
Its often far easier to read other people's code
than the code you write yourself.
The brain skip things.

c.savur

@mrjj said:

Super
that was a nice reduction :)
Its often far easier to read other people's code
than the code you write yourself.
The brain skip things.

Yes, you are right.
Looking at a function is much easier than looking at 1000 lines of code :)

Thank you again, for your help.

mrjj

@c.savur
U are most welcome
Indeed it is.
I used for work at a publishing house.

I could read my page of text over and over. Like 50 times.
Then I gave it to the proof reader and she found some errors
anyway :)