aseprite/docs/files/ase.txt

ASE Files (.ASE) Format description
Copyright (C) 2004-2009 by David Capello
----------------------------------------------------------------------

1. References
2. Introduction
3. Header
4. Frames
5. New chunk types
6. File Format Changes

========================================
1. References
========================================

ASE files use Intel (little-endian) byte order.

BYTE		An 8-bit unsigned integer value
WORD		A 16-bit unsigned integer value
DWORD		A 32-bit unsigned integer value
LONG		A 32-bit signed integer value
BYTE[n]		"n" bytes.
RECT		Four LONGs (in the order: x-pos, y-pos, width, heigth)
STRING		length=WORD (how many characters to read next)
                string=BYTE[length]
		The \0 character isn't included.
PIXEL		Pixel format:
		- In RGB images, each pixel have 4 bytes in
                  this order Red, Green, Blue, Alpha.
		- In Grayscale images, each pixel have 2 bytes
                  in the order Value, Alpha.
		- In Indexed images, each pixel uses 1 byte (the index).


========================================
2. Introduction
========================================

The format is much like FLI/FLC files, but with different magic number
and differents chunks.  Also, the color depth can be 8, 16 or 32 for
Indexed, Grayscale and RGB respectively, and the images are more easy
to read (there aren't differences with old frames).  The palette isn't
included for color depths more than 8, but when the sprite is 8 bpp,
the palette is in a FLI color chunk (it could be type=11 or type=4).
See fli.txt for details.

To read the sprite, just do this:
* Read the ASE header (section 3)
* For each frame do (how many frames? the ASE header has that
  information):
  + Read the frame header (section 4)
  + For each chunk in this frame (how many chunks? the frame header
    has that information)
    - Read the chunk (it should be layer information, a cel or a
      palette)


========================================
3. Header
========================================

A 128-byte header (same as FLC/FLI header, but with other magic
number):

DWORD		File size
WORD		Magic number (0xA5E0)
WORD		Frames
WORD		Width in pixels
WORD		Height in pixels
WORD		Color depth (bits per pixel)
		32 bpp = RGBA
		16 bpp = Grayscale
		 8 bpp = Indexed
DWORD		Flags (must be 0)
WORD		Speed (milliseconds between frame, like in FLC files)
		DEPRECATED: You should use the frame duration
                            field from each frame header
DWORD		Set be 0
DWORD		Set be 0
DWORD		Ignore this field
WORD		Number of colors (0 means 256 for old sprites)
BYTE[94]	For future (set to zero)


========================================
4. Frames
========================================

After the header come the "frames" data. Each frame has this little
header of 16 bytes:

  DWORD		Bytes in this frame
  WORD		Magic number (always 0xF1FA)
  WORD		Number of "chunks" in this frame
  WORD		Frame duration (in milliseconds)
  BYTE[6]	For future (set to zero)

Then each chunk format is:

  DWORD		Chunk size
  WORD		Chunk type
  BYTE[]	Chunk data


========================================
5. New chunk types
========================================

Layer Chunk (0x2004)
----------------------------------------

  In the first frame should be a set of layer chunks to determine the
  entire layers layout:

  WORD		Flags:
		  LAYER_IS_READABLE	= 0x0001
		  LAYER_IS_WRITABLE	= 0x0002
		  LAYER_IS_LOCKMOVE	= 0x0004
		  LAYER_IS_BACKGROUND	= 0x0008
  WORD		Layer type (0=normal (image) layer, 1=layer set)
  WORD          Layer child level (see NOTE.1)
  WORD		Default layer width in pixels (ignored)
  WORD		Default layer height in pixels (ignored)
  WORD		Blend mode (always 0 for layer set)
                  BLEND_MODE_NORMAL     = 0
                  BLEND_MODE_DISSOLVE   = 1
		  BLEND_MODE_MULTIPLY   = 2
		  BLEND_MODE_SCREEN     = 3
		  BLEND_MODE_OVERLAY    = 4
		  BLEND_MODE_HARD_LIGHT = 5
		  BLEND_MODE_DODGE      = 6
		  BLEND_MODE_BURN       = 7
		  BLEND_MODE_DARKEN     = 8
		  BLEND_MODE_LIGHTEN    = 9
		  BLEND_MODE_ADDITION   = 10
		  BLEND_MODE_SUBTRACT   = 11
		  BLEND_MODE_DIFFERENCE = 12
		  BLEND_MODE_HUE        = 13
		  BLEND_MODE_SATURATION = 14
		  BLEND_MODE_COLOR      = 15
		  BLEND_MODE_LUMINOSITY = 16
		  BLEND_MODE_COPY       = 17
  BYTE[4]	For future (set to zero)
  STRING	Layer name


Cel Chunk (0x2005)
----------------------------------------

  This chunk determine where to put a cel in the specified
  layer/frame.

  WORD		Layer index (see NOTE.2)
  WORD		X position
  WORD		Y position
  BYTE		Opacity level
  WORD		Cel type
  BYTE[7]	For future (set to zero)

  + For cel type = 0 (Raw Cel):

    WORD	Width in pixels
    WORD	Height in pixels
    PIXEL[]	Raw pixel data: row by row from top to bottom,
                for each scanline read pixels from left to right.

  + For cel type = 1 (Linked Cel):

    WORD	Frame position to link with

  + For cel type = 2 (compressed image):

    WORD	Width in pixels
    WORD	Height in pixels
    BYTE[]	Compressed "Raw Cel" data. Details about the
                compression method: 
                http://www.ietf.org/rfc/rfc1951.txt


Mask Chunk (0x2016) DEPRECATED
----------------------------------------

  WORD		X position
  WORD		Y position
  WORD		Width
  WORD		Height
  BYTE[8]	For future (set to zero)
  STRING	Mask name
  BYTE[]	Bit map data (size = height*((width+7)/8))
                Each byte contains 8 pixels (the leftmost pixels are
		packed into the high order bits)


Path Chunk (0x2017)
----------------------------------------

  Never used.


Notes
----------------------------------------

NOTE.1: The child level is used to show the relationship of this
        layer with the last one read, for example:

  Layer name and hierarchy	Child Level
  -----------------------------------------------
  - Background			0
    `- Layer1			1
  - Foreground			0
    |- My set1			1
    |  `- Layer2		2
    `- Layer3			1


NOTE.2: The layer index is a number to identify any layer in the
        sprite, for example:

  Layer name and hierarchy	Layer index
  -----------------------------------------------
  - Background			0
    `- Layer1			1
  - Foreground			2
    |- My set1			3
    |  `- Layer2		4
    `- Layer3			5


========================================
File Format Changes
========================================

  1) The first change from the first release of the new .ase format,
     is the new frame duration field. This is because now each frame
     can have different duration.

     How to read both formats (old and new one)?  You should set all
     frames durations to the "speed" field read from the main ASE
     header.  Then, if you found a frame with the frame-duration
     field > 0, you should update the duration of the frame with
     that value.

  2) The format of ASE 0.6 beta has a header with a background color
     after the two last reserved DWORD

     ...
     WORD	Speed (milliseconds between frame, like in FLC files)
     DWORD	Set be 0
     DWORD	Set be 0
     DWORD	Background-color          <------ *
     BYTE[96]	For future (set to zero)

     * This field is deprecated, and now it should be 0 or his value
       should be completely ignored. The only drawback is that the
       sprite will have a transparent background instead of a colored
       one.