ILBMdt 47.7

IFF ILBM picture datatype 47.7

Short:        IFF ILBM picture datatype 47.7
Author:       Henryk Richter
Uploader:     henryk richter gmx net (Henryk Richter)
Type:         util/dtype
Version:      47.7
Architecture: m68k-amigaos >= 3.0.0
Distribution: NoCD

 Introduction

 This is yet another datatype for IFF ILBM pictures. My primary
 motivatior for this datatype is that I ran into some issues 
 loading a number of IFF pictures by my favorite datatypes 
 based viewer and decided to find a solution for these pictures.

 This ILBM datatype supports 1-8 bitplanes including EHB and HAM
 in V42 (non RTG) mode. In presence of RTG and/or picture.datatype 
 V43 or later, 24 Bit images are supported as well. In addition,
 planar color mapped data and HAM images are loaded into FastRAM 
 and internally promoted to chunky representation with active RTG 
 in order to conserve ChipRAM. Some routines are implemented in 
 Assembler to provide a good loading speed.

 This datatype also handles some of the known issues with ILBM
 images generated by certain software like Adobe Photoshop.

 In addition to regular ILBM images, this datatype also provides
 support for dynamic palettes which are generated by tools like
 HAMLab or HAM_convert into PCHG or SHAM chunks.


 Installation

 At most two files need to be copied for installation: the
 datatypes descriptor (ILBM) and the datatype class 
 (ilbm.datatype). You might want move the existing files to
 a safekeeping place (e.g. SYS:Storage/Datatypes/). A reboot
 is usually required to enable the new datatype.

 From CLI:
 Copy Classes/Datatypes/ilbm.datatype Sys:Classes/Datatypes/
 Copy Devs/Datatypes/ILBM Devs:Datatypes/

 From WB:
 Drag the ILBM icon from Devs/Datatypes of this distribution
 to SYS:Devs/Datatypes and drag Classes/Datatypes/ilbm.datatype
 to SYS:Classes/Datatypes.


 Troubleshooting

  Malformed IFF ILBM files

   Some slightly malformed IFF ILBM files are known that they 
   can be loaded in popular imaging programs but sometimes fail 
   to be recognised by datatypes. In such cases, stringent checks
   in Datatypes.library and IFFParse.library alongside the 
   requirement to actually rely on these two libraries prevent 
   the invocation of ilbm.datatype. 

   This package contains a commandline tool called "fixiff"
   which is able to fix some commonly encountered problems with
   IFF ILBM files. It takes two arguments. The first argument
   is the input file and the second argument is the resulting
   copy.

   Example: fixiff Workbench:broken_iff.iff ram:fixed_iff.iff

   The fixiff tool will correct incorrect IFF FORM header sizes,
   convert out-of-spec run-length encoding to valid encoding,
   trim extra data and fill up incomplete BODY data with zeros. 

   The latest fixiff got additional switches: 
   NOMASK will omit the mask in the output 
   ADDGRAB converts a masked picture into a brush.
   SETTRANS=0 (or any other valid pen) will designate a transparent
              color

 CPU compatibility

 The datatype is an all-in-one binary for any 68k Amiga. Some
 68020+ optimizations are enabled at runtime, if applicable.



 History
 47.7 - fixed potential crash with >8 Bitplane files that claim
        to be HAM
      - updated fixiff to auto-delete HAM and EHB flags in >8 Bit
        ILBM files

 47.6 - dynamic HiRes and dynamic HAM support (PCHG,SHAM) by
        promoting such images to 24 bit (V43 picture.datatype)

 47.5 - Mask support in 24 Bit mode
      - Transparency masks will only be handed to picture.datatype
        for brush type IFFs (i.e. some pictures contain a mask plane
	that is actually a drawing stencil)

 47.4 - Replaced Datatypes descriptor (DEVS:Datatypes/ILBM) by
        a different variant that relies on pattern matching 
	instead of detection code. This fixes issues with
	clipboard operations. Datatypes.library 45.4 now likes
	the new descriptor, too.

 47.3 - first Aminet release