Spectrum 512 - Revision history

Ivo: no plainlinks

2008-05-02T00:45:18Z

no plainlinks

← Older revision		Revision as of 17:45, 1 May 2008
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	~~<span class="plainlinks">~~
	* Company: [[Trio Inc.]] / [[Antic Software]]		* Company: [[Trio Inc.]] / [[Antic Software]]
	* Extensions: .spu, .spc, sps		* Extensions: .spu, .spc, sps
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	[[Category:Atari ST Image Formats]]		[[Category:Atari ST Image Formats]]
	[[Category:Image Formats]]		[[Category:Image Formats]]
	~~</span>~~

Ivo: category atari st image formats

2008-05-02T00:19:17Z

category atari st image formats

← Older revision		Revision as of 17:19, 1 May 2008
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	[[Image:Atarist_lowres.png]]		[[Image:Atarist_lowres.png]]

			[[Category:Atari ST Image Formats]]
	[[Category:Image Formats]]		[[Category:Image Formats]]
	</span>		</span>

Ivo: /* Palettes */ empty line --> space, so the code shows as one block

2008-04-27T21:27:55Z

Palettes: empty line --> space, so the code shows as one block

← Older revision		Revision as of 14:27, 27 April 2008
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	int find_index(unsigned int x, unsigned int c) {		int find_index(unsigned int x, unsigned int c) {
	unsigned int t = 10 * c;		unsigned int t = 10 * c;

	if (c&1) t -= 5;		if (c&1) t -= 5;
	else t++;		else t++;

	if (x < t) return c;		if (x < t) return c;
	if (x >= t+160) return c + 32;		if (x >= t+160) return c + 32;

Ivo: /* Palettes */ describe palette switching per scanline

2008-04-27T21:27:13Z

Palettes: describe palette switching per scanline

← Older revision		Revision as of 14:27, 27 April 2008
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	==Palettes==		==Palettes==

			Spectrum 512 files use three palettes per scanline. Because of the Atari ST's limitted graphics capabilities, a trick was used to change the hardware color palette twice per scanline. Given an x-coordinate and a color index, the following algorithm returns the corresponding spectrum palette index (0-47).

			int find_index(unsigned int x, unsigned int c) {
			unsigned int t = 10 * c;

			if (c&1) t -= 5;
			else t++;

			if (x < t) return c;
			if (x >= t+160) return c + 32;
			return c + 16;
			}

	==Image Data==		==Image Data==

Ivo: describe smooshed format

2008-04-27T21:17:43Z

describe smooshed format

← Older revision		Revision as of 14:17, 27 April 2008
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	* Extension: .sps		* Extension: .sps

			typedef spectrum512_smooshed_file {
			uint16_t magic; /* "SP" */
			uint16_t reserved; /* always 0 */
			uint32_t data_length;
			uint32_t palette_length;
			uint8_t data[];
			uint8_t palettes[];
			} spectrum512_smooshed_file;

			The image data is compressed similar to .spc files.

			There's a second variant where the data is not encoded plane by plane and line by line, but in byte wide vertical stripes (for each plane (for each column (scanline 1-199))).

			It is unknown how (or impossible) to distinguish the two variants.

			The palettes are compressed similar to .spc files, but rather than uint16_t values, variable length codes are stored.
			Each palette consists of a 14-bit map which marks which entries will follow (entries 0 and 15 are skipped and set to black).
			After the map, zero or more codes of 9-bits follow.

	==Palettes==		==Palettes==

Ivo: extensions

2008-04-27T21:05:54Z

extensions

← Older revision		Revision as of 14:05, 27 April 2008
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	__TOC__		__TOC__
	==Spectrum 512 Uncompressed==		==Spectrum 512 Uncompressed==

			* Extension: .spu

	typedef spectrum512_file {		typedef spectrum512_file {
Line 16:		Line 18:

	==Spectrum 512 Compressed==		==Spectrum 512 Compressed==

			* Extension: .spc

	typedef spectrum512_compressed_file {		typedef spectrum512_compressed_file {
Line 46:		Line 50:

	==Spectrum 512 Smooshed==		==Spectrum 512 Smooshed==

			* Extension: .sps

	==Palettes==		==Palettes==

Ivo: describe compressed format

2008-04-27T16:42:22Z

describe compressed format

@@ Line 16: / Line 16: @@
 ==Spectrum 512 Compressed==
 ==Spectrum 512 Smooshed==
@@ Line 22: / Line 50: @@
 ==Image Data==
-The image data is stored in a planar format.
+Uncompressed image data (.spu files) is stored in a planar format.
 [[Image:Atarist_lowres.png]]

Ivo: move generic remark up

2008-04-27T16:24:42Z

move generic remark up

← Older revision		Revision as of 09:24, 27 April 2008
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	'''Spectrum 512''' was an image drawing program for the [http://en.wikipedia.org/wiki/Atari_ST Atari ST].		'''Spectrum 512''' was an image drawing program for the [http://en.wikipedia.org/wiki/Atari_ST Atari ST].

			16-bit words are stored in big-endian order.

	__TOC__		__TOC__
	==Spectrum 512 Uncompressed==		==Spectrum 512 Uncompressed==

	~~16-bit words are stored in big-endian order.~~

	typedef spectrum512_file {		typedef spectrum512_file {

Ivo: create spectrum 512 page

2008-04-27T16:23:19Z

create spectrum 512 page

New page

<span class="plainlinks">
* Company: [[Trio Inc.]] / [[Antic Software]]
* Extensions: .spu, .spc, sps

'''Spectrum 512''' was an image drawing program for the [http://en.wikipedia.org/wiki/Atari_ST Atari ST].

__TOC__
==Spectrum 512 Uncompressed==

16-bit words are stored in big-endian order.

typedef spectrum512_file {
uint16_t data[16000]; /* first 80 words (first scanline) is unused and should be zeroes */
uint16_t palettes[199 * 3 * 16]; /* 199 scanlines, 3 palettes per scanline, 16 entries per palette */
} spectrum512_file;

==Spectrum 512 Compressed==

==Spectrum 512 Smooshed==

==Palettes==

==Image Data==
The image data is stored in a planar format.

[[Image:Atarist_lowres.png]]

[[Category:Image Formats]]
</span>