[DUG] Resizing images

[John Bird]

Here is an example.....shows the original larger image and the resized one. 
You can see the ragged border when the image is on a darker background,  as 
the offending pixels are not the same as the transparent colour of the rest 
of the square image out to the edges - they have been altered in colour by 
the resizing.   Hope I am making sense.

The original image was a png, and it has been resized then converted to BMP 
using Irfanview. As far as I recall I didn't use the Lanczos option, just 
the defaults.

http://sites.google.com/site/jbclnz2/delphistuff/delphimiscissues

John

----- Original Message ----- 
From: "Conor Boyd" <Conor.Boyd at trimble.co.nz>
To: "NZ Borland Developers Group - Delphi List" <delphi at delphi.org.nz>
Sent: Tuesday, January 19, 2010 11:31 AM
Subject: Re: [DUG] Resizing images


> What I think you're seeing (without seeing your example) is the softness
> introduced by most resampling algorithms (when used for downsampling).
>
> Something like Bicubic Sharper in PS or Lanczos Kernel in Irfanview
> might help.
>
> However, most of these sharpening algorithms probably work better on
> photographic images than they will on graphics.  Maybe a more "dumb"
> program like Paint would resample a graphic better.  Or reducing the
> color depth of the image before resizing will also help.
>
> Post an example, and I'll see what I would do with it.
>
> C.
>
> -----Original Message-----
> From: delphi-bounces at delphi.org.nz [mailto:delphi-bounces at delphi.org.nz]
> On Behalf Of John Bird
> Sent: Tuesday, 19 January 2010 11:15 a.m.
> To: NZ Borland Developers Group - Delphi List
> Subject: Re: [DUG] Resizing images
>
> More specifically - does the GIMP or any other resizing method allow me
> to specify this?:
>
> Where say an image with a a white background (the transparent colour)
> meets a grey border, and the image is resized (especially if resized
> smaller), there will be on this edge a new pixel that has part of the
> grey border and
> the white background.   Most resizing operations will change the pixel
> to
> light grey/cream whereas I want to tell it to either use the original
> grey or the white background only for any pixels on the edge.
>
> John
>
>> The GiMP is always handy for image manipulation.  Generally I draw my
>> images in a really old version of Corel Draw, then use GiMP for
>> transparance, shadows and so on.
>>
>
>
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