Setting a single pixel?

Have you had a look here. Hope it may help

As you probably know, FF works with sample coordinates, not with pixel coordinates - so there isn't really a simple way to set pixel values like you would on a bitmap based system.

You can use the global variables OUTPUT_WIDTH and OUTPUT_HEIGHT to get the image dimensions in pixels and use those calculate the pixel coordinates.

For example:

Code
function prepare()    px,py = get_slider_input(PX),get_slider_input(PY)    w,h = OUTPUT_WIDTH, OUTPUT_HEIGHT    px,py = math.floor(px*w), math.floor(py*h) end; function get_sample(x, y)    local v = 0    if math.floor(x*w) == px and math.floor(y*h) == py then v = 1 end;    return v,v,v end;

Note that this only works with square images. Some extra code is needed to compensate for different aspect ratios.

Thanks emme, that basically does what I want but due to the sample coordinates system you mention your script steps a bit too much each pixel value increased and also when the input value is max it seems to make the pixel vanish.

Another thing I noticed is if you don't use a slider input and just set px,py = 1,1 instead then the pixel vanishes. Also how would you increase the pixel size from 1x1 to say 10x10?

My goal was to port some lua scripts that draw various things using a set pixel function but it seems that due to the sample coordinates system there would be problems.

Also thanks for the reply Rachel Duim, currently I only have FF version 3 so I can't check the map script that filter uses. The script emme posted is basically what i want but there is the few issues I mention.

Thanks emme, that code makes the pixel disappear if set to 0,0 however but I fixed it using an if statement:

Code

function prepare()    px,py = get_slider_input(PX),get_slider_input(PY)    w,h = OUTPUT_WIDTH, OUTPUT_HEIGHT    px,py = math.floor(px*w), math.floor(py*h) end; function get_sample(x, y)    local r = 0    local g = 0    local b = 0    local a = 1    if px == 0 and py == 0 then       if math.floor(x*w) == px and math.floor(y*h) == py then          r = 255          g = 0          b = 0          a = 1       end;    else       if math.ceil(x*w-0.5) == px and math.ceil(y*h-0.5) == py then          r = 255          g = 0          b = 0          a = 1       end;    end;        return r,g,b,a end;

I made a script where I convert the setPixel part into a function but for me it doesn't work in FF3, possibly due to the fractional values thing. Could someone confirm if the following script works in later versions?

Code
function prepare()    w,h = OUTPUT_WIDTH, OUTPUT_HEIGHT end; function setPixel(x1,y1,w,h,px,py,r,g,b,a)    px2,py2 = math.floor(px*w), math.floor(py*h)    if math.floor(x1*w) == px2 and math.floor(y1*h) == py2 then    end;    return r,g,b,a end function get_sample(x, y)    local r = 0    local g = 0    local b = 0    local a = 1    setPixel(x,y,w,h,1,1,255,0,0,1)    return r,g,b,a end;

If it doesn't work in later versions perhaps my code is broken somehow but it looks as if it should work.

Edit - Maybe the developers could a a new node "Pixel Script" in FF11 which can correctly set pixels and maybe also do html5 canvas style things like drawing lines and rectangles etc with simple code. That would allow for all sorts of interesting scripts to be made.

Thanks that show me an output.