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| Rev | Author | Line No. | Line |
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| 2 | daniel-mar | 1 | |
| 2 | ART FILES BY IMAGINATION PILOTS |
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| 3 | Technical overview by Daniel Marschall 15 Feb 2018 |
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| 4 | |||
| 5 | |||
| 6 | VERSION 1.x (16-bit era, "IPE16") |
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| 7 | ================================= |
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| 8 | |||
| 9 | Version 1.0 For game: "Blown Away" (1994) |
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| 10 | * File signature "Art" + 20 NUL bytes |
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| 11 | * Image names up to 23 characters |
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| 12 | (unsure if the 23th byte must be a zero terminator) |
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| 13 | * LZW implementation: GIF standard implementation |
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| 14 | - variable code length between 9 and 12 bits |
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| 15 | - clear code (256) |
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| 16 | - end code (257) |
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| 17 | * Pictures can only be 8-bit |
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| 18 | * Each picture can either be LZW compressed (code "P") |
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| 19 | or uncompressed (code "p", lower case) |
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| 20 | * Decompressed/raw data: Top-down pixel data |
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| 21 | * Attached: Optional palette (R,G,B), uncompressed. |
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| 22 | (Sprites usually do not have a palette, so the game |
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| 23 | will use the palette of the parent picture) |
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| 24 | |||
| 25 | Version 1.1 For games: "Panic in the Park" (1995) |
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| 26 | "Where's Waldo? At the Circus" (1995) |
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| 27 | * Codes for compression/raw are now "Q" and "q" instead of |
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| 28 | "P" and "p" |
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| 29 | * Each picture has now a relative X- and Y-offsets for 'fine-tuning'. |
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| 30 | These offsets cannot be negative, though. |
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| 31 | |||
| 32 | VERSION 2.x (32-bit era, "IPE32") |
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| 33 | ================================= |
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| 34 | |||
| 35 | Version 2.0 For games: "Where's Waldo? Exploring Geography" (1996) |
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| 36 | "Eraser Turnabout" (1997) |
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| 37 | "Virtual K'Nex" (1998) |
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| 38 | * File signature "ART_DATA" |
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| 39 | * Image names up to 8 characters; |
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| 40 | no zero termination required after the 8 characters. |
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| 41 | * LZW implementation by Mark R. Nelson and Shawn M. Regan |
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| 42 | - variable code length between 9 and 13 bits |
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| 43 | - clear code (256) |
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| 44 | - end code (257) |
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| 45 | * Pictures are divided into chunks. Each chunk can be compressed or |
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| 46 | uncompressed. Limitations: |
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| 47 | - Each compressed chunk (except the last one) must decode into |
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| 48 | exactly 16382 (0x3FFE) bytes of uncompressed data. |
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| 49 | - The size of the compressed data of a chunk must not exceed the |
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| 50 | size of the original uncompressed data. |
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| 51 | * The size of each chunk (raw or compressed) is limited |
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| 52 | to max. 32767 Bytes (0x7FFF). |
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| 53 | * Decompressed/raw data: Windows Bitmap (without file header); |
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| 54 | therefore, theoretically every color depth/compression/etc. can be used. |
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| 55 | For 8-bit pictures, the palette is included in the Bitmap. |
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| 56 | * Re-using of parent palette is not possible. |