Colour Manipulation

jonathandlynch at jonathandlynch at
Sat Mar 18 17:03:14 EDT 2017

With 10 million pixels, comparing 3 different base colors (RGB), and checking both upper and lower bounds, that comes to 60 million comparisons. That is an awful lot for a scripted environment.

You would need to make an external (and, frankly, the LC instructions on making desktop externals do not work for modern versions of LC and Visual Studio).

For a project, I was able to successfully use ImageMagick as a command line image processor. It took a few seconds, but much better than what LC took.

ImageMagick is pretty flexible and might give you what you need. I was using it for green screen image extractions.

Sent from my iPhone

> On Mar 18, 2017, at 2:20 PM, Peter Reid via use-livecode <use-livecode at> wrote:
> I've got an app that allows the user to display an image using a variable number of colours (2-24 colours).  In addition, the user can specify upper and lower thresholds so that all pixels below a specified value are displayed using a colour such as black and all pixels with values above a specified value are displayed using a colour such as red.  Pixels with values between the thresholds are displayed using the specified colour range of 2-24 colours. The images can consist of up to 8-10 million pixels, they are rectangular and can be in a landscape or portrait orientation.
> Whilst I have this working the code that manages the changing of the number and use of colours in an image is rather slow.  This is despite me using the "repeat for each" loop structure and lock the screen wherever possible to get the maximum speed!
> Does anyone have any clever algorithms, code, add-ons, etc. that can do this kind of thing in a flash?!
> Thanks
> Peter
> --
> Peter Reid
> Loughborough, UK
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