U++ forum: Welcome to the forum

Search on this site

Search in forums

Home » U++ Library support » Draw, Display, Images, Bitmaps, Icons » Rescale and copy area of source image into an area of dest image

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Rescale and copy area of source image into an area of dest image [message #14547]

Sun, 02 March 2008 20:32

mdelfede
Messages: 1308
Registered: September 2007

Ultimate Contributor

I could not manage to do an apparently simple stuff : copy a rectangular area on source image, rescale it and put in another rectangular area on a destination imagebuffer.

This is my piece of code :

// extract and rescale image area
ImageEncoder t;
Rescale(t, destSize, page, sourceRect);
// copies rescaled image inside cache rectangle
const RGBA *rgba = t;
for(int iLine = 0 ; iLine < t.GetHeight(); iLine++)
{
	Copy(imageCache[i+rect.top]+rect.left, rgba, t.GetWidth());
	rgba += t.GetWidth();
}

or :

// extract and rescale image area
ImageEncoder t;
Rescale(t, destSize, page, sourceRect);
Image img = Image(t);
// copies rescaled image inside cache rectangle
const RGBA *rgba = img;
for(int iLine = 0 ; iLine < img.GetHeight(); iLine++)
{
	memmove(imageCache[i+rect.top]+rect.left, rgba, img.GetWidth()* sizeof(RGBA));
	rgba += img.GetWidth();
}

And many other options, but no way, destination stuff doesn't contain the required copy. I know that 't' contains a valid image because painting it directly is ok.

Any hint ?

Ah, last stuff.... ImageDraw class (which could be used for this purpose....) is documented in help with many member functions that it doesn't have in reality, first of them the constructor

ImageDraw(Image &)

Ciao

Max

[Updated on: Sun, 02 March 2008 22:50]

Report message to a moderator

Re: Rescale and copy area of source image into an area of dest image [message #14554 is a reply to message #14547]

Mon, 03 March 2008 17:52

mdelfede
Messages: 1308
Registered: September 2007

Ultimate Contributor

well, partly solved... the bug was not here... for others interested in using Image and Imagebuffer, beware :

ImageBuffer buf;
Draw d = ........
...........
...........
d.DrawImage(buf, .....)

will *not* work, or better, it'll work ONCE.
DrawImage expects an Image& parameter, so buf is converted on the fly onto Image object, loosing its content due to destroy-on-copy behaviour.
The correct code is :

ImageBuffer buf;
Draw d = ........
...........
...........
Image img = buf;
d.DrawImage(img, .....)
buf = img;

quite un-intuitive, indeed. It would be much better to have a different version of DrawImage with an ImageBuffer & as first parameter. Also, allowing such automatic type conversion on objects that have the destroy-on-copy semantics can lead to subtle bugs...

Ciao

Max

Report message to a moderator

Re: Rescale and copy area of source image into an area of dest image [message #14556 is a reply to message #14554]

Mon, 03 March 2008 18:37

masu
Messages: 378
Registered: February 2006

Senior Member

Hi Max,

can't you just use it like this:

ImageBuffer buf;
Draw d = ........
...........
...........
d.DrawImage(Image(buf), .....)

?

Matthias

Report message to a moderator

Re: Rescale and copy area of source image into an area of dest image [message #14575 is a reply to message #14556]

Mon, 03 March 2008 21:32

mdelfede
Messages: 1308
Registered: September 2007

Ultimate Contributor

masu wrote on Mon, 03 March 2008 18:37

Hi Max,

can't you just use it like this:

ImageBuffer buf;
Draw d = ........
...........
...........
d.DrawImage(Image(buf), .....)

?

Matthias

mhhhh.. I think it'll not work, as imagebuf get still converted on a temporary image, so it loses its contents.

Max

Report message to a moderator

Re: Rescale and copy area of source image into an area of dest image [message #14578 is a reply to message #14575]

Mon, 03 March 2008 23:11

masu
Messages: 378
Registered: February 2006

Senior Member

Max, I think you are right.
The documentation says, conversion clears buffer when converted to image and vice versa.

Matthias

Report message to a moderator

Previous Topic:	Drawing and scrolling
Next Topic:	Problem with offset

Goto Forum:

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Sun May 11 15:05:04 CEST 2025

Total time taken to generate the page: 0.02670 seconds