Crack Art - Revision history

Ivo: no plainlinks

2008-05-02T00:42:13Z

no plainlinks

← Older revision		Revision as of 17:42, 1 May 2008
Line 1:		Line 1:
	~~<span class="plainlinks">~~
	* Company: Detlef Röttger & Jan Borchers		* Company: Detlef Röttger & Jan Borchers
	* Extensions: .ca1, .ca2, .ca3		* Extensions: .ca1, .ca2, .ca3
Line 75:		Line 74:
	[[Category:Atari ST Image Formats]]		[[Category:Atari ST Image Formats]]
	[[Category:Image Formats]]		[[Category:Image Formats]]
	~~</span>~~

Ivo: category image formats

2008-05-02T00:16:33Z

category image formats

← Older revision		Revision as of 17:16, 1 May 2008
Line 72:		Line 72:

	[[Image:Atarist_lowres.png]]		[[Image:Atarist_lowres.png]]


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

Ivo: test subcategory

2008-05-02T00:10:27Z

test subcategory

← Older revision		Revision as of 17:10, 1 May 2008
Line 74:		Line 74:


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

Ivo: describe decompression algorithm; pseudocode

2008-05-02T00:04:24Z

describe decompression algorithm; pseudocode

← Older revision		Revision as of 17:04, 1 May 2008
Line 23:		Line 23:

	==Decompression algorithm==		==Decompression algorithm==

			Yet another [[RLE]] variant:

			data[0] == ESCape character
			data[1] == initial value (fill screen memory with this value)

			data[2]<<8 + data[3] == offset, this value is constantly added to the current byte position in order to
			find the next byte position. If the position >= 32000, it jumps back to
			the first unwritten byte position (initial write is not taken into account).
			This is used to 'jump' through the data and accomplish plane-by-plane compression.

			data[4 ....] == RLE compressed data

			[pseudocode]

			while (!eof et cetera) {
			a = data[x++]

			if (a != ESC) output a, continue

			b = data[x++]

			if (b == ESC) output ESC, continue

			c = data[x++]

			if (b == 2) {
			if (!c) break /* end decompression */
			c << 8
			c += data[x++]
			skip c+1 bytes, continue /* or output c+1 times initial_value */
			}
			if (b == 1) {
			c <<= 8
			c += data[x++]
			}
			if (b <= 1) { /* 0 and 1 */
			d = data[x++]
			output c+1 times d, continue
			}

			output b times c /* b>2 && b!= ESC */
			}

	==Uncompressed data format==		==Uncompressed data format==

Ivo: uncompressed image data format

2008-05-01T23:33:38Z

uncompressed image data format

← Older revision		Revision as of 16:33, 1 May 2008
Line 19:		Line 19:
	uint8_t data[]		uint8_t data[]
	} crackart_file;		} crackart_file;

			If the file is uncompressed, sizeof(data) == 32000 bytes of raw video memory.

	==Decompression algorithm==		==Decompression algorithm==

	==Uncompressed data format==		==Uncompressed data format==

			The image data is stored in a planar format.

			[[Image:Atarist_lowres.png]]


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

Ivo: file format

2008-05-01T23:28:26Z

file format

← Older revision		Revision as of 16:28, 1 May 2008
Line 13:		Line 13:

	typedef crackart_file {		typedef crackart_file {
			uint16_t magic; /* "CA" */
			uint8_t compressed; /* 0 = no compression, 1 = compressed */
			uint8_t resolution; /* 0 = low (320x200x16), 1 = medium (640x200x4), 2 = high (640x400x2) */
			uint16_t palette[palsize]; /* palsize = 16 (low res), 4 (med res) or 0 (high res) */
			uint8_t data[]
	} crackart_file;		} crackart_file;

Ivo: template for crack art format; link to assembly compression and decompression routines

2008-05-01T23:24:54Z

template for crack art format; link to assembly compression and decompression routines

New page

<span class="plainlinks">
* Company: Detlef Röttger & Jan Borchers
* Extensions: .ca1, .ca2, .ca3

Crack Art was an image drawing program for the [http://en.wikipedia.org/wiki/Atari_ST Atari ST].
Here are the m68k assembly [http://ivop.free.fr/multimediawiki/CA_PACK.S compression] and [http://ivop.free.fr/multimediawiki/CA_UNPAC.S decompression]
routines, provided by the original program.

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

__TOC__
==File format==

typedef crackart_file {
} crackart_file;

==Decompression algorithm==

==Uncompressed data format==

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