[Qt-interest] How can I read a large image fastly?

[Jason H]

Also, Why are you using QImage? QPixmap is faster (QImage is device independent) and make sure you are using premultiplied ARGB.




----- Original Message ----
From: Kermit Mei <kermit.mei at gmail.com>
To: Jason H <scorp1us at yahoo.com>
Cc: qt-interest <qt-interest at trolltech.com>
Sent: Thu, February 4, 2010 9:30:02 AM
Subject: Re: [Qt-interest] How can I read a large image fastly?

Jason H wrote:
> You can;t speed loading, but you can load it into memory then use QPixmap::copy() to access/scale,etc only the visible area.
> 
> 
> Or are you trying to scale the thing in entirety?
> There are a couple scaling algorithms. Also avoid use of SmoothPixmapTransform,as you'll be doing sub-pixel interpolation.
>  
<snip>

Dear Jason,
     Would you like to give me more details about it? I don't know how to deal with it as what you told me to.
For example:
1.How to load it in memory first? QPixmap::load() ? This is more slower then QImage::load().

2.What "scaling algorithms"  should I use?

Thanks.
B.R
Kermit