Proposal: New !DATA meta-command for embedded textures

[Travis Cobbs]

Note: this is in response to this thread.

This is a proposal to add a new !DATA meta-command that can be used to embed texture data into model files (for use with unofficial parts in an OMR model). The proposed specification for the new meta-statement follows. Please discuss.

Purpose

This document describes the !DATA meta-statement, which contains a set of commands for embedding binary data into LDraw files.

New meta-statement token

!DATA

This is the main data-embedding meta-command.

Reuse of existing meta-statement token

!:

This will be used to specify a BASE-64 encoded data stream. This token was introduced with the !TEXMAP meta-statement, and will be reused here for three reasons: its reuse will not interfere with its use in !TEXMAP; it is useful for the same reasons that it was useful in !TEXMAP; and !DATA is only useful right now for embedding texture data for use with !TEXMAP, so the two meta-statements are related to each other.

Syntax

0 !DATA START
0 !: <data1>
0 !: <data2>
...
0 !: <datan>
0 !DATA END

Description

This meta-statement allows for BASE-64 encoded data to be used inside a multi-part-dat (MPD) file. The decoded binary data replaces of the embedded MPD sub-file.

1. This meta-statement must come after the 0 FILE meta-statement signifying a sub-file in a multi-part-dat (MPD) file.
   
2. The FILE that the DATA belongs to must not contain any geometry.
   
3. The FILE must contain one and only one DATA section.
   
4. The FILE may contain header information.
   
5. All characters after 0 !: that are not valid BASE-64 characters must be ignored. (This is intended to allow white-space characters to be placed in the line, but still applies to all other characters that are not valid BASE-64 characters.)
   
6. Each 0 !: line except for the last must contain exactly 76 encoded characters.
   
7. The last 0 !: line must contain no more than 76 encoded characters.
   

Example

0 FILE main.ldr
0 Author: Roland Melkert
1 15  -40 -20 0  1 0 0  0 0 1  0 1 0 plane.dat

0 FILE plane.dat
0 plane texmap test
0 UNOFFICIAL PART
0 BFC NOCERTIFY

0 !TEXMAP START PLANAR  0 0 0  40 0 0  0 0 40  checker123yyz.png
4 16  0 0 0  40 0 0  40 0 40  0 0 40
0 !TEXMAP END

0 FILE checker123yyz.png
0 !DATA START
0 !:iVBORw0KGgoAAAANSUhEUgAAAQAAAAEACAYAAABccqhmAAAABmJLR0QA/wD/AP+gvaeTAAAACXBI
0 !:WXMAAC4jAAAuIwF4pT92AAAAB3RJTUUH3gcbDhUzUyNxeQAAArVJREFUeNrt3cENwzAMBMFjoM7d
0 !:p6vIX2lBeRECZzo4GFjIL9ZOdhpVeu3dOj9VZb/9bT4BxhIAEABAAAABAAQAEABAAAABAAQAEABA
0 !:AAABAAQAEABAAAABAAQAEABAAAABAAQAEABAAAABAAQAEABAAAABAAQAEADgX5Wk9UC6+/T22+8F
0 !:AAgAIACAAAACAAgAIACAAAACAAgAIACAAAACAAgAIACAAAACAAgACAAgAIAAAAIACAAgAIAAAAIA
0 !:CAAgAIAAAAIACABwgeU+u/32z93vBQB+AQABAAQAEABAAAABAAQAEABAAAABAAQAEABAAAABAAQA
0 !:EABAAAABAAQAEABAAAABAAQAEABAAAABAAQAEABAAAABAI4t99l79z9p3v/6/pP3ewGAXwBAAAAB
0 !:AAQAEABAAAABAAQAEABAAAABAAQAEABAAAABAAQAEABAAAABAAQAEABAAAABAAQAEABAAAABAAQA
0 !:EABAAIBjy3324fu/8f0H7/cCAL8AgAAAAgAIACAAgAAAAgAIACAAgAAAAgAIACAAgAAAAgAIACAA
0 !:gAAAAgAIACAAgAAAAgAIACAAgAAAAgAIACAAgAAAxypJ64H06ffZ7bffCwAQAEAAAAEABAAQAEAA
0 !:AAEABAAQAEAAAAEABAAQAEAAAAEABAAQABAAQAAAAQAEABAAQAAAAQAEABAAQAAAAQAEABAA4ArL
0 !:fXb77Z+73wsA/AIAAgAIACAAgAAAAgAIACAAgAAAAgAIACAAgAAAAgAIACAAgAAAAgAIACAAgAAA
0 !:AgAIACAAgAAAAgAIACAAgAAAAgAcqyStB9Ldp7fffi8AQAAAAQAEABAAQAAAAQAEABAAQAAAAQAE
0 !:ABAAQAAAAQAEABAAQABAAAABAAQAEABAAAABAAQAEABAAAABAAQAEABAAIAL/AB/0mJQmotO+gAA
0 !:AABJRU5ErkJggg==
0 !DATA END