convert Integers to RGB values and back with Python
Solution 1
Both functions seem to be working fine.
The max value expressed by a 24 bit integer (forget the sign for now) is
mx = pow(2,24)-1 # i.e. 16777215
So
i1 = 2147483647
is higher than mx
and
colr1 = getRGBfromI(i1)
correctly gives
(255, 255, 255) # better to view it in hex as 0xFFFFFF
since it cuts out the bits higher than 24 (0xFFFFFF occupies bits from 0 to 23)
Viceversa,
i2 = getIfromRGB(colr1)
correctly gives
16777215
which is the max value you can represent with 24 bits (i.e. the mx
above).
If you pour 1.4 litres of water in a 1L bottle, some water will be lost in the overflow. When you empty the bottle, you will find 1L at max
Solution 2
There's nothing wrong with your code. The values are different, because you are giving 2147483647 as input, which, translated to hexadecimal, gives 0x7FFFFFFF
as an output. On the other hand, 16777215 is 0xFFFFFF
in hexadecimal, so you understand there is nothing wrong with your code actually, apart from the fact that you are giving such a big decimal number as an input.
You can test this if you type:
print i1 & 0xFFFFFF, i2 # this will return equal values
M_PF
Updated on July 09, 2022Comments
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M_PF almost 2 years
I have two functions, one to return RGB values from a given Integer, and the other function does the reverse, providing it with RGB values it returns an Integer. I'm testing this by seeing if the integer i convert to RGB turns back from RGB into the original integer value, but I'm getting different values.
def getRGBfromI(RGBint): blue = RGBint & 255 green = (RGBint >> 8) & 255 red = (RGBint >> 16) & 255 return red, green, blue def getIfromRGB(rgb): red = rgb[0] green = rgb[1] blue = rgb[2] print red, green, blue RGBint = (red<<16) + (green<<8) + blue return RGBint
the test:
i1 = 2147483647 colr1 = getRGBfromI(i1) print colr1 # returns (255,255,255) i2 =getIfromRGB(colr1) print i1, i2 # returns 2147483647 16777215
To me it seems like the getRGBfromI() is correct and the getIfromRGB() is incorrect, but I may be wrong about that too.
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M_PF over 8 yearsi assumed the upper limit was 2147483647 but that works if i'm using 32bits (for an ARGB value) and here Im only using 24 (RGB). My mistake is in the input not the code. thanks for pointing that out.
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Pynchia over 8 yearsa quick note: in
getIfromRGB
you can make the code clearer and more concise withred, green, blue = rgb
instead using indexes on the tuple.