[REBOL] do %image.png

[Jason Cunliffe]

do %image.png

My objective is to implement a roundtrip toolkit with /Core and /View
interfaces for embedding, extracting and running REBOL scripts embedded in
images. Then the real fun can begin!

I have made a little progess:
A tiny hardcoded test is now working :-)

buddha.png is a PNG image file with a REBOL script embedded in it.
http://www.postcardscience/rebol/buddha.png

I used TweakPNG (Win32only) to learn about PNG and inset my REBOL script.
http://entropymine.com/jason/tweakpng/

By design I insert a special keyword "REBOLscript" after the "tEXt" chunk to
help parsing. Also, a special REBOL end of script marker ";EOF" at the end
of test script itself.  The helps parsing the REBOL script end from other
data or padding in the PNG file.

It takes about 6 seconds to store 29kb image file as a string on a 500Mhz
PIII Win98se Vaio laptop.

Lots of features and funtions to implement.
But first I need some basic advice:

Q1. How can I improve the time to load PNG into a rebol string?
Q2. What other approach do you suggest than the one I am following?

thanks for any feedback
- Jason

========================
REBOL [ File: %buddha.r]

;download or read from http://www.postcardscience/rebol/buddha.png

buddha: read/binary %buddha.png

b: "" for i 1 length? buddha 1 [append b to-char buddha/:i]
; 7 seconds for 29Kb image on 500MhzPIII

; head b ; make sure we are at the beginning when debugging in REBOL shell

search-key: "tEXtREBOLscript"      ; better than just looking for "REBOL"
header-key: "REBOL "               ; space after REBOL should mean it's the
header
tail-key:   ";EOF"                 ; by design, this marks end of REBBOl
script

; later probably will want to include #!path-to-rebol and find those first

b: find next b search-key   ; start of our tEXt chunk containing REBOL
script
b: find next b header-key   ; start of the script
start-mark: length? b       ; how many bytes to end of PNG file

bend: find next b tail-key            ; end of script
end-mark: length? bend               ; how many bytes to chop off
script-length: start-mark - end-mark  ; how many bytes to use of 'script

script: ""
for i 1 script-length 1 [append script b/:i] ; chop the end off so we have
pure script
write %buddha-script.r script                ; save it to file

do %buddha-script.r                          ; test it!

-- 
To unsubscribe from this list, please send an email to
[EMAIL PROTECTED] with "unsubscribe" in the 
subject, without the quotes.