Re: mapping a pixel to a character


j0mbolar wrote:
> I have access to the pixels of an image in grayscale.
> I would like to map each pixel to a character.
> I have 64 characters arranged in order based on
> their densities. What is a technique that would
> perform this kind of mapping?
>
> There are also 24 bits per pixel and 3 bytes per
> pixel.
>

>>From section 4.5 of:

http://www.jgcampbell.com/ip/ip4.txt

Your input image is f1. Suppose, a<=f1(x,y)<=b, i.e. the range of f1()
is [a,b], and you
want the range mapped to z0<=z'<=G, then the transformation is

(4.5-2) z'= (zG-z0).(z-a)/(b-a) + z0

= (zG-z0).z/(b-a) + (z0.b-zG.a)/(b-a)
scale shift

Your [a, b] is [0, 63]; round or truncate the value to an integer and
you have an index into a character array -- i.e. put the grey level
characters in an array. If you want, I have some very kludgy C code
that prints an image as a page of characters; but I could never find
more than ten suitable. On a line printer, one could do overstrike, so
i think i managed 24 grey levels with that.

Assuming that is what you mean. Initially I thought OCR was your goal.

Best regards,

Jon C.

.

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