Path: chuka.playstation.co.uk!news
From: James Russell <James_Russell@scee.sony.co.uk>
Newsgroups: scea.yaroze.programming.2d_graphics
Subject: Re: Get pixel
Date: Thu, 30 Jul 1998 13:31:49 +0100
Organization: Sony Computer Entertainment Europe
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Antony Arciuolo wrote:
> 
> My real question is can I directly access the frame buffer (a short
> GetPixel(short X, short Y) function) and how can I use this to reference
> the palette of the puddle so I can use palette collision detection?

unsigned short GetPixel(short X, short Y) {
	static RECT getPixelRect = { 0, 0, 1, 1 }; // x=y=0, w=h=1.
	unsigned short returnVal;

	getPixelRect.x = X;
	getPixelRect.y = Y;
	StoreImage(&getPixelRect,&returnVal);
	DrawSync(0);
	returnVal = (returnVal << 8) | (returnVal >> 8);
	return	returnVal;
}

Notes:

o	X and Y are Frame Buffer coordinates, not screen coordinates.
o	A StoreImage is just a GPU command, and hence is put in the GPU queue (see the new FAQ on
	the main page for more info), so the StoreImage is not executed until everything else in
	the queue has been processed. That's why you have to do a DrawSync (which waits for the
	GPU to finish), because if you don't, then returnVal will contain a junk number.
o	VRAM is stored in big-endian order, not little-endian. So I do some bit shifting to
	turn it into a number that you'd expect.
o	Don't expect this method to be fast. 


> How are references laid out in the frame buffer since I assume all graphics
> are translated into 16-bit for the final screen plotting?

Yup.

-- 
== James_Russell@scee.sony.co.uk                +44 (171) 447-1626
== Developer Support Engineer - Sony Computer Entertainment Europe

#'M ST#P#D        "I'd like to buy a vowel, Pat. An `O' please."