MASK LFD Resource Type
Author: Jagged Fel (jaggedfel621@gmail.com)
Site: http://idmr.empirereborn.net
Updated: 2009.10.05
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The MASK resource is image data found primarily in cockpit LFD files. These
files do not contain RMAPs, although are comprised of a PANL, MASK and PLTT.
The MASK is a monochrome image which tells the program where "empty" pixels
are so that you can actually see out of the cockpit.

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MASK Structure

The following values are used through this and all of my file definitions
unless otherwise specified:
NAME	LENGTH	DESC
----	------	----
BYTE	1	unsigned 8-bit
CHAR	1	ASCII character
SHORT	2	signed Int16
INT	4	signed Int32

--
Header
Row[]
SHORT	Reserved (0)
--

struct Header (size 0x10)
{
	0x0	CHAR[4]	"MASK"
	0x4	CHAR[8]	Name
	0xC	INT	Length
}

struct Row
{
	BYTE	StartPixel
	BYTE[]	Ranges
}

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MASK Details

Unlike most image resources found in the LFDs, MASK does not have a Width and
Height defined in the resource itself. The size is defined in the cockpit .INT
file under the appropriate view subsection. The sizes can be determined
computationally, although complicated mask patterns increase the difficulty of
determining the image size correctly.

The StartPixel value is either 01 or FF, and decides which color the first Range
will be. 01 starts black, FF starts white.

Range values are the length of pixels to be the current color. So if a row
starts as 01 32 40 05, then the row will be 50px black, 64px white, 5px black.
But what happens when you need more than 255px? The Range value of 00 adds 256
to the next value, and they can be stacked. So a row of FF 00 00 80 is 640px of
white (256 + 256 + 128).

Important note: A row cannot contain a Range of 256px (00) or 512 (00 00), for
there is no following value for the 00 to be added to. The only exception is
if the row *ends* in a zero Range. In this case, typically a 01 is used as a
"throw away" pixel. In GUNBT08.LFD, the MASK therein contains a line of
FF 00 80 00 01 which comes out to 641px, instead of the 640px of the image.
The extra pixel is not displayed, though it must be accounted for while
processing the image (TIEEdit does not, and will display the MASK incorrectly).

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