Message-ID:	<002501be09c7$ebc8cd60$d1acf482@win95.swipnet.se>
From:	"Ulrik Sunnvius aka Keso - \"Be strong, be wrong!\"" <keso-98 AT swipnet DOT se>
To:	<djgpp AT delorie DOT com>
Subject:	Re: How do I detect a RLE-sprite on a bitmap?
Date:	Fri, 6 Nov 1998 21:56:25 +0100
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Reply-To:	djgpp AT delorie DOT com

You see my problem is that aliens shoot randomly at the RLE-sprite, 
and then I want some way to find out if the shoot (vline(..)) has hit the RLE-
sprite. If hit, the shoot should disappear, and the "hero" dies.. 

Hmm... mayby I can get the x value, but i need to know the y-value where the 
sprite begins (the shoot shouldn't continue..).

I hope you can help me. If not, thanks anyway!

/US
------------------------------
+46 70 3695091
http://start.at/cprog/
keso-98 AT swipnet DOT se
------------------------------ 

>> 1. How do I detect (i.e. where it is on the bitmap) a RLE-sprite on a
>> bitmap? (getpixel() don't work...)
>>
>> (2. How do I detect a regular sprite on a bitmap?)
>> (3. How do I detect a little bitmap on a bitmap?)
>
>Sorry, what are you trying to do? If you want to know where an RLE sprite is
>on a bitmap, wouldn't you know already as you've just placed it there?
>
>If you're thinking of comparing two images to find an area of one image
>which is the same as the other image, don't use RLE sprites unless you want
>to make your job 20 times more complex. A very much simplified algortihm
>could be:
>
>1. Use getpixel on the larger bitmap scanning across until you find a pixel
>the same colour as the top-left pixel of the sprite.
>
>2. Check the next pixels on the line in turn. Compare these to the sprite
>image. If you find a pixel out of place return to step one.
>
>You've got to repeat this many times.
>
>James Arthur
>jaa AT arfa DOT clara DOT net
>ICQ#15054819
>
>

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