Re: seeking for help on MNG creation

> In general, I would tend to test (current versions of) libmng over
> pngcheck, but be aware that the latter shows an invalid length for
> the BACK chunk:

BACK chunk's fine. Spec-wise it can be 6,7,9 or 10 bytes long. 9 or 10 means 
there's a background image-id (and optionally a tiling parm).

The main problem is the remainder of the file. Here's a snapshot of a MNGeye 
dump:

MHDR: Width=320 Height=240 Ticks=1000 Layercount=0 Framecount=3 Frametime=600 Simplicity=7
  tEXt: "title"="Blinkenlights Movie"

  DEFI: Id=1 NoShow=0 Concrete=0 PosX=0 PosY=0

  IHDR: Width=320 Height=240 BitDepth=8 ColorType=2 Compress=0 Filter=0 Interlace=0
    IDAT: RawSize=74127
  IEND: 

  BACK: Red=#0000 Green=#0000 Blue=#0000 Mandatory=3 ImageId=256 Tiling=0
  SAVE: 
  TERM: Termination=3 Iteration=0 Delay=0 Iter.Max=0x7FFFFFFF
  SEEK: Keyword=""

  FRAM: Mode=4 Name="" C-Delay=2 Delay=200

  DEFI: Id=2 NoShow=0 Concrete=0 PosX=0 PosY=0

  IHDR: Width=70 Height=11 BitDepth=8 ColorType=2 Compress=0 Filter=0 
Interlace=0
    IDAT: RawSize=1600
  IEND: 

  CLON: Source=2 Clone=3 Type=1 Show=0 Concrete=1 P-Type=0 PosX=84 
PosY=36
  CLIP: First=3 Last=3 C-Type=0 C-Left=144 C-Right=36 C-Top=154 C-
Bottom=47
  CLON: Source=2 Clone=4 Type=1 Show=0 Concrete=1 P-Type=0 PosX=94 
PosY=36
  CLIP: First=4 Last=4 C-Type=0 C-Left=154 C-Right=36 C-Top=164 C-
Bottom=47
  CLON: Source=2 Clone=5 Type=1 Show=0 Concrete=1 P-Type=0 PosX=104 
PosY=36
  CLIP: First=5 Last=5 C-Type=0 C-Left=164 C-Right=36 C-Top=174 C-
Bottom=47
  CLON: Source=2 Clone=6 Type=1 Show=0 Concrete=1 P-Type=0 PosX=144 
PosY=36
  CLIP: First=6 Last=6 C-Type=0 C-Left=204 C-Right=36 C-Top=214 C-
Bottom=47
  CLON: Source=2 Clone=7 Type=1 Show=0 Concrete=1 P-Type=0 PosX=154 
PosY=36
  CLIP: First=7 Last=7 C-Type=0 C-Left=214 C-Right=36 C-Top=224 C-
Bottom=47
  CLON: Source=2 Clone=8 Type=1 Show=0 Concrete=1 P-Type=0 PosX=164 
PosY=36
  CLIP: First=8 Last=8 C-Type=0 C-Left=224 C-Right=36 C-Top=234 C-
Bottom=47
  CLON: Source=2 Clone=9 Type=1 Show=0 Concrete=1 P-Type=0 PosX=74 
PosY=53
  CLIP: First=9 Last=9 C-Type=0 C-Left=134 C-Right=53 C-Top=144 C-
Bottom=64
  CLON: Source=2 Clone=10 Type=1 Show=0 Concrete=1 P-Type=0 PosX=84 
PosY=53
  CLIP: First=10 Last=10 C-Type=0 C-Left=144 C-Right=53 C-Top=154 C-
Bottom=64
  CLON: Source=2 Clone=11 Type=1 Show=0 Concrete=1 P-Type=0 PosX=94 
PosY=53
  CLIP: First=11 Last=11 C-Type=0 C-Left=154 C-Right=53 C-Top=164 C-
Bottom=64

As you can see he CLIP values do not match with the X/Y values of the 
cloned image. Apart from the somewhat dubious use of CLON in this way (I'd 
suggest using MOVE/SHOW; preferably inside a LOOP/ENDL whenever 
possible), you'll need to align those parameters. The images are actually being 
displayed but since they fall outside of the clipping parms (also note the 
probable swap of the right- and top-clipping!), nothing will change on the 
screen.

Gerard


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