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Re: Reading the dimensions of a sprite or JPEG on disk

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In article <59f119bd97Paul@sprie.nl>,
   Paul Sprangers <Paul@sprie.nl> wrote:
> In article <ZeadnfdmIvFTZAn_nZ2dnUU7-WfNnZ2d@brightview.co.uk>,
>    Gerald Holdsworth <nospam@hollypops.co.uk> wrote:

> > RISC OS 5.29 may be able to handle, and convert, JPEGs natively.
> > !Paint can certainly import a JPEG and output a Sprite, and it
> > can also export a JPEG. 

> Yes, I know. And both !ArtWorks and !DPlingScan can perfectly
> resize any bitmap as well. But the point is that I want to do it
> myself - or better: I don't want to force possible users of my
> program to be dependent of those (commercial) programs. And I want
> to figure out how those programs do it...


> > I'd have a hunt around the RO5 PRMs to see if there is anything,
> > or post on the ROOL forums.

> I did find some related posts on the ROOL forum, but not helpful
> enough for me to tackle the problem. Probably I will have to admit
> that the WIMP is too complex for me.

I do not think it is the Wimp that is your problem.

Earlier you said...
> The images come from disk, typically photographs. So, not from a
> file, nor from another application.

... but any image that is dragged from disc *is* a file!

I suspect your problem with sprites is that a sprite file can (and
usually does) contain several sprites. The information about each one
is scattered throughout the file - there is no handy list at the
beginning. So after a drag of a sprite file, you first have to find a
list of the sprites within, then the details of each one ... then
decide which one is required. Which probably entails loading the whole
file into memory.

This is unlike a jpeg file, which simply contains one jpeg.

-- 
Martin Avison 
Note that unfortunately this email address will become invalid
without notice if (when) any spam is received. 

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Thread

Reading the dimensions of a sprite or JPEG on disk Paul Sprangers <Paul@sprie.nl> - 2022-05-28 12:08 +0200
  Re: Reading the dimensions of a sprite or JPEG on disk News <chrisjohnson@spamcop.net> - 2022-05-28 11:37 +0100
    Re: Reading the dimensions of a sprite or JPEG on disk Paul Sprangers <Paul@sprie.nl> - 2022-05-28 12:48 +0200
      Re: Reading the dimensions of a sprite or JPEG on disk Gerald Holdsworth <nospam@hollypops.co.uk> - 2022-05-28 14:26 +0100
        Re: Reading the dimensions of a sprite or JPEG on disk Paul Sprangers <Paul@sprie.nl> - 2022-05-30 13:58 +0200
          Re: Reading the dimensions of a sprite or JPEG on disk Gerald Holdsworth <nospam@hollypops.co.uk> - 2022-05-30 15:16 +0100
            Re: Reading the dimensions of a sprite or JPEG on disk Paul Sprangers <Paul@sprie.nl> - 2022-05-30 16:51 +0200
              Re: Reading the dimensions of a sprite or JPEG on disk Gerald Holdsworth <nospam@hollypops.co.uk> - 2022-05-30 18:07 +0100
                Re: Reading the dimensions of a sprite or JPEG on disk Paul Sprangers <Paul@sprie.nl> - 2022-05-31 09:27 +0200
                Re: Reading the dimensions of a sprite or JPEG on disk Gerald Holdsworth <nospam@hollypops.co.uk> - 2022-05-31 12:12 +0100
                Re: Reading the dimensions of a sprite or JPEG on disk Paul Sprangers <Paul@sprie.nl> - 2022-05-31 15:30 +0200
                Re: Reading the dimensions of a sprite or JPEG on disk Gerald Holdsworth <nospam@hollypops.co.uk> - 2022-05-31 21:51 +0100
                Re: Reading the dimensions of a sprite or JPEG on disk Steve Fryatt <news@stevefryatt.org.uk> - 2022-05-31 23:29 +0100
                Re: Reading the dimensions of a sprite or JPEG on disk Martin Wuerthner <spamtrap@mw-software.com> - 2022-06-07 16:33 +0200
                Re: Reading the dimensions of a sprite or JPEG on disk Paul Sprangers <Paul@sprie.nl> - 2022-06-11 08:56 +0200
                Re: Reading the dimensions of a sprite or JPEG on disk Sprow <news@sprow.co.uk> - 2022-06-12 08:15 -0700
                Re: Reading the dimensions of a sprite or JPEG on disk Martin <News03@avisoft.f9.co.uk> - 2022-05-31 13:10 +0100
                Re: Reading the dimensions of a sprite or JPEG on disk Paul Sprangers <Paul@sprie.nl> - 2022-05-31 15:59 +0200
                Re: Reading the dimensions of a sprite or JPEG on disk News <chrisjohnson@spamcop.net> - 2022-05-31 16:28 +0100
                Re: Reading the dimensions of a sprite or JPEG on disk News <chrisjohnson@spamcop.net> - 2022-05-31 16:51 +0100
                Re: Reading the dimensions of a sprite or JPEG on disk Paul Sprangers <Paul@sprie.nl> - 2022-05-31 18:33 +0200

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