imageformats : PBM and XPM

[Zardoz89]

Haver you planed to support PBM and XPM formats ? They are very trivial, and are very useful for embed small image resources on code.

[rikkimax]

I've just had a look at XPM and PBM formats, I wouldn't mind PBM and family, but XPM not really.
Right now PNG is the only one implemented as a reference implementation, but I think I could do PBM some time soon.

[Zardoz89]

PBM it's very trivial to implement. I wrote a PBM reader on C++ some time ago to generate a bitmap font from it.

[rikkimax]

Yeah, that's what I thought as well.
Unfortunately to do XPM properly it looks like you need a c lexer. Which I do have, but I know will never go into Phobos.

[Zardoz89]

XPM have different versions .

The original version , really need a more complex parsing. It was design to be used with a #include "image.xpm" from C.

XPM2 not have these C stuff . If you check XPM2, It's similar to PBM :

! XPM2
48 4 2 1
a c #FFFFFF
b c #000000
abaabaababaaabaabababaabaabaababaabaaababaabaaab
abaabaababaaabaabababaabaabaababaabaaababaabaaab
abaabaababaaabaabababaabaabaababaabaaababaabaaab
abaabaababaaabaabababaabaabaababaabaaababaabaaab

XPM3 isn't hard to parse, as the only C stuff is at the begin/end of the file :

/* XPM */
static char * XFACE[] = {
/* <Values> */
/* <width/cols> <height/rows> <colors> <char on pixel>*/
"48 4 2 1",
/* <Colors> */
"a c #ffffff",
"b c #000000",
/* <Pixels> */
"abaabaababaaabaabababaabaabaababaabaaababaabaaab",
"abaabaababaaabaabababaabaabaababaabaaababaabaaab",
"abaabaababaaabaabababaabaabaababaabaaababaabaaab",
"abaabaababaaabaabababaabaabaababaabaaababaabaaab"
};

If you remove the opening/end, is a list of strings and uses // & /* */ as comments.

[rikkimax]

I'm happy with XPM2 just not the others.
For now I'm happy with XPM having the status "to be implemented by community", just like JPEG.

At the current time, I won't be implementing another file format any where close to PNG's complexity, ones enough for now.

I'll see what I can do in the next few hours about PBM support.

[docandrew]

I've started on the XPM work - trying to mirror the PNG interface as much as possible. Plan is to start with XPM2 and then do a version of XPM1/3 that doesn't use the full C lexer if I can pull it off.

[rikkimax]

Don't worry too much about what I have with PNG. Get something working e.g. using GC and all.
Then let's worry about getting it good quality.

[docandrew]

OK that's encouraging - I've been trying to make sense of the allocator work and interfaces, it's a lot to take in!

[rikkimax]

Lets just say my first go of png reader/writer was quite a bit different.
https://github.com/Devisualization/image/tree/master/source/png/devisualization/image/png

[docandrew]

Making good progress. Initially I'll have a "D-ized" XPM1 and XPM3 that basically take raw D strings to make it easy for people to embed the XPM in their D code.

Reading external .xpm with the valid C syntax will be a little more work but will definitely not require a full C lexer.

I think the format is used rarely, and not really intended for high-performance image manipulation, so a lot of optimization is probably unnecessary.

One question for you rikkimax: is there an image or bitmap class you'd prefer me to use for the export/internal representation? I poked around the repository source and had a hard time finding something with an obvious API that I should use.

[rikkimax]

They are provided by std.experimental.graphic.image.storage.
They all satisfy isImage and the default for PNG is horizontal.

Hard code it for now to be e.g. horizontal. I have a solution for that in PNG that'll work fine here as well.