OpenEuphoria

1. Scaling images

• Posted by Jonas Temple <jtemple at yhti.net> Nov 22, 2004
• 2362 views
• Last edited Nov 23, 2004

Since graphics in Windows is my weak spot...how does one scale an image
(BMP, PNG, JPEG, etc.) such that when the image is shrunk by the user
it doesn't look funny?  What I mean by "funny" is that I have a window
that displays an image (using FreeImage).  I want to show the image in
the window for a "preview" so I use the stretchBlt function in 
Win32Lib to shrink the image.  But the shrunken image does not look as
good as say, shrinking the image in the Windows Picture and Fax Viewer in
XP.

Can this be done with stretchBlt or is more complicated than that?


Jonas Temple
http://www.yhti.net/~jktemple

3. Re: Scaling images

• Posted by Alexander Toresson <toressonodakra at swipnet.se> Nov 22, 2004
• 2316 views
• Last edited Nov 23, 2004

Jonas Temple wrote:
> 
> Since graphics in Windows is my weak spot...how does one scale an image
> (BMP, PNG, JPEG, etc.) such that when the image is shrunk by the user
> it doesn't look funny?  What I mean by "funny" is that I have a window
> that displays an image (using FreeImage).  I want to show the image in
> the window for a "preview" so I use the stretchBlt function in 
> Win32Lib to shrink the image.  But the shrunken image does not look as
> good as say, shrinking the image in the Windows Picture and Fax Viewer in
> XP.
> 
> Can this be done with stretchBlt or is more complicated than that?
> 

Here's a way to do perfect scaling-down of images, using only a nearest-
neighbour scaling routine and a mosaic (square) effect:

You first have to scale the original picture up to make the width and 
height a multiple of the destination picture's size, and bigger than 
the original. Ie if the original is 1024x768, and the destination is 
100x100, you'll have to scale it to 1100x800. For this operation,
linear interpolation helps, but ain't necessary.

Then we'll apply the mosaic effect, with a size of 
(width / dest_width)x(height / dest_height), in this example 11x8.

Then we just have to scale it down to the wanted size.

Regards, Alexander Toresson

Shhh! Be vewy quiet! I'm hunting wuntime ewwows!

5. Re: Scaling images

• Posted by Alexander Toresson <toressonodakra at swipnet.se> Nov 22, 2004
• 2335 views
• Last edited Nov 23, 2004

Jonas Temple wrote:
> 
> Alexander Toresson wrote:
> > 
> > > Since graphics in Windows is my weak spot...how does one scale an image
> > > (BMP, PNG, JPEG, etc.) such that when the image is shrunk by the user
> > > it doesn't look funny?  What I mean by "funny" is that I have a window
> > > that displays an image (using FreeImage).  I want to show the image in
> > > the window for a "preview" so I use the stretchBlt function in 
> > > Win32Lib to shrink the image.  But the shrunken image does not look as
> > > good as say, shrinking the image in the Windows Picture and Fax Viewer in
> > > XP.
> > > 
> > > Can this be done with stretchBlt or is more complicated than that?
> > > 
> > 
> > Here's a way to do perfect scaling-down of images, using only a nearest-
> > neighbour scaling routine and a mosaic (square) effect:
> > 
> > You first have to scale the original picture up to make the width and 
> > height a multiple of the destination picture's size, and bigger than 
> > the original. Ie if the original is 1024x768, and the destination is 
> > 100x100, you'll have to scale it to 1100x800. For this operation,
> > linear interpolation helps, but ain't necessary.
> > 
> > Then we'll apply the mosaic effect, with a size of 
> > (width / dest_width)x(height / dest_height), in this example 11x8.
> > 
> > Then we just have to scale it down to the wanted size.
> > 
> 
> That all sounds good...I was hoping for a code example, though!  
> 
> Got one?   :)
> 

No, not at the moment. I'll code one. Anyway, I do not know the win32 api,
and doing it in eu may be too slow. I don't know if the win32 api
features a mosaic function. I'll code one 100% eu anyway.
I assume it's a 24-bit bitmap kept in a sequence, that is to be
processed.

/Lex

Shhh! Be vewy quiet! I'm hunting wuntime ewwows!

7. Re: Scaling images

• Posted by Jonas Temple <jtemple at yhti.net> Nov 22, 2004
• 2319 views
• Last edited Nov 23, 2004

Alexander Toresson wrote:
> No, not at the moment. I'll code one. Anyway, I do not know the win32 api,
> and doing it in eu may be too slow. I don't know if the win32 api
> features a mosaic function. I'll code one 100% eu anyway.
> I assume it's a 24-bit bitmap kept in a sequence, that is to be
> processed.
> 
Alexander,

Actually, if you look at the reply from Brian Broker he provided an
example that worked perfectly on WinXP!

Jonas Temple
http://www.yhti.net/~jktemple

9. Re: Scaling images

• Posted by petersalvatore Jun 27, 2013
• 2125 views

Nice sharing. But I have never used the tools you mentioned above. ANd I also think that using CODE to scale images is a headache work.

As for myself, I used to scale images with the help of another image SDK.

It is just one of many but I do appreciate its simple way of processing.

Even though I only tried its free trial package to generate barcodes and didn′t check the cost and licensing conditions, it works great for me.

Share with you. And I will try your sharing later.

Thanks again.

Best regards, Peter