What does step do? Also, changing single pixel colors?

[Josh1910]

Hi,

I'm trying to use a stack to change individual pixel colors (surprising challenge with LiveCode). Anyway, one stack that I'm experimenting with has a word "step" in the repeat loop "repeat with i = 1 to tLength step 4".

My silly question is what is step doing? It's not in help or the dictionary. Is it jumping by 4 steps at a time?

Secondary, if someone happens to know how to change a pixel color (I'm trying to sprinkle black pixels on a white square), that'd be great.

Josh

[Martin Koob]

Hi

Yes it is jumping through every 4th value in the range you specify in step.

Put the following on a button and put a field on the card and try this.

Code: Select all

on mouseUp
   repeat with i = 1 to 100 step 4
      put i & CR after tList
   end repeat
   put tList into field 1
end mouseUp

You can also step backwards by giving a negative value for step.

Code: Select all

on mouseUp
   repeat with i = 100 to 1 step -4
      put i & CR after tList
   end repeat
   put tList into field 1
end mouseUp

Not sure how to change a pixel colour though.

Martin Koob

[Martin Koob]

I just had a song pop into my head....

+ goes add
- goes subtract
repeat goes around and around again

mouseDown goes Cli..
mouseUp goes ..ick
return goes back
breakpoint goes stop so you can see what wrong

put goes in
so does set
but what I don't know is....

What does the step do?

Ring a ding ding ding a ding ding a ding
etc......


Maybe Jacque can add LiveCode songs to her LiveCode poetry page....

Martin

[dunbarx]

Hi.

I could answer this, but would rather have you go to the dictionary for "repeat" and look through the comments near the "with" loopForm.

The mouseColor returns the color of the current pixel. You want to set that pixelColor? You cannot set, say, the color of a single pixel on a card. The various colors of features of controls can be set, but you would have to have a rectangle graphic of 1x1 and set its backColor or maybe the borderColor.

Craig Newman

[jacque]

You can manipulate image pixels in all sorts of ways, so if the square is a white image this lesson may give you some ideas:
http://lessons.livecode.com/m/4071/l/126613

There are some other lessons on image processing too, you could try a search through the lessons.

@Martin: I didn't think anyone ever found my personal experimental pages.

[FourthWorld]

This thread contains some super-wonderful image manipulation tools:
http://forums.livecode.com/viewtopic.php?f=10&t=9490

[Martin Koob]

@Martin: I didn't think anyone ever found my personal experimental pages.

@jacque: I had lost the bookmark but with a few google searches I found it. 'LiveCode Haiku Jacque' does the trick.
http://www.jacque.on-rev.com

As far as the song I had just listened to this 'What does the fox say' parody so the tune was going through my head when I read the post.
https://www.youtube.com/watch?v=aEi_4Cyx4Uw

I thought to promote the release of LiveCode 8 it would make a great youTube video. "What does the step do?"

It could be an open source project. People could contribute more lyrics. Someone could host it on git hub, track revisions. I am sure there are a few musicians and singers in the community. And of course the dance moves would be done by Kevin and the LiveCode HQ engineers and staff, in kilts of course, stepping out, up and down the Royal Mile in Edinburgh. If that doesn't go viral what will?

Martin