generalize grey scale value advice

rayzun

I need 2 see about this ...

an image has been adjusted into a grey scale.
I have every rgb/hex value :

EFEFEF
EEEEEE
EDEDED
ECECEC
EBEBEB
EAEAEA
E9E9E9
E8E8E8
E7E7E7
E6E6E6
E5E5E5
E4E4E4
E3E3E3
E2E2E2
E1E1E1
E0E0E0
DFDFDF
DEDEDE
DDDDDD
DCDCDC
DBDBDB
DADADA
D9D9D9
D8D8D8
D7D7D7
D6D6D6
D5D5D5
D4D4D4
D3D3D3
D2D2D2
D1D1D1
D0D0D0
CFCFCF
CECECE
CDCDCD
CCCCCC
CBCBCB
CACACA
C9C9C9
C8C8C8
C7C7C7
C6C6C6
C5C5C5
C4C4C4
C3C3C3
C2C2C2
C1C1C1
C0C0C0
BFBFBF
BEBEBE
BDBDBD
BCBCBC
BBBBBB
BABABA
B9B9B9
B8B8B8
B7B7B7
B6B6B6
B5B5B5
B4B4B4
B3B3B3
B2B2B2
B1B1B1
B0B0B0
AFAFAF
AEAEAE
ADADAD
ACACAC
ABABAB
AAAAAA
A9A9A9
A8A8A8
A7A7A7
A6A6A6
A5A5A5
A4A4A4
A3A3A3
A2A2A2
A1A1A1
A0A0A0
9F9F9F
9E9E9E
9D9D9D
9C9C9C
9B9B9B
9A9A9A
8F8F8F
8E8E8E
8D8D8D
8C8C8C
8B8B8B
8A8A8A
7F7F7F
7E7E7E
7D7D7D
7C7C7C
7B7B7B
7A7A7A
6F6F6F
6E6E6E
6D6D6D
6C6C6C
6B6B6B
6A6A6A
5F5F5F
5E5E5E
5D5D5D
5C5C5C
5B5B5B
5A5A5A
999999
989898
979797
969696
959595
949494
939393
929292
919191
909090
898989
888888
878787
868686
858585
848484
838383
828282
818181
808080
797979
787878
777777
767676
757575
747474
737373
727272
717171
707070
696969
686868
676767
666666
656565
646464
636363
626262
616161
606060
595959
585858
575757
565656
555555

I ask where seperation lies .216 browser safe colors ?
generalize 4 columns etc...

alimadzi

Not exactly sure what you're asking, but I'll take a shot anyway...

The traditional browser safe colors are drawn from six values of red, six green, and six blue. The possible values are: 00, 33, 66, 99, CC, FF. I'm assuming you know that in a hex color code the first two are red, next two green, and last two blue. So some examples of browser safe colors would be 0033FF, 6699CC, FFCC33, etc.

So probably what you want to do is write a function that rounds all the colors you've provided to their nearest browser safe color. Am I on the right track here?

rayzun

I think you have the best method described. If at all any examples on how to write such a function ??

alimadzi

rayzun wrote:
I think you have the best method described. If at all any examples on how to write such a function ??

Sure, I'll get you started. You need to take each hex color and split it into three chunks of two characters each. Then use this function on each chunk...

http://www.php.net/manual/en/function.hexdec.php

Then round each resulting decimal number to the nearest multiple of 33 and use this function to change it back to hexadecimal...

http://www.php.net/manual/en/function.dechex.php

Then concatenate the three chunks together again into a websafe hex color. Let us know if you run into any problems with this...

rayzun

very clever to me once your advice worked.
.still thinking about working function . ... .

but .online tool that is similair
http://easycalculation.com/decimal-converter.php

alimadzi

Not sure what you're saying. Are you still going to write a PHP script to do this or using the online tool 100 times?

rayzun

well, Im learning a bit... The whole idea is .. output a large text blog from MySQL
using browser safe colors. Originally, if only using grey it would be much simpler.

but with your direction, Ive seen some examples, that maybe I can go with all 216 colors.

However, with just grey's, I would use the online tool # times, then use

   $txt = str_replace ("61", "63", $txt);
   $txt = str_replace ("62", "63", $txt);

.I think that would work well enough

alimadzi

Yikes! Please don't tell me you're thinking of doing this manually. Or writing hundreds of string replacement conditions. Let me get you started on a better solution...

<?php

$originalColors = array( 'EFEFEF', 'EEEEEE', 'EDEDED', 'ECECEC', 'EBEBEB' );
$browserSafe = array( );

foreach ( $originalColors as $color ) {
    // get decimal equivalent of individual colors
    $red = hexdec( substr( $color, 0, 2 ) );
    $green = hexdec( substr( $color, 2, 2 ) );
    $blue = hexdec( substr( $color, 4, 2 ) );

// round colors to nearest browser safe color
$red = round( $red / 33 ) * 33;
$green = round( $green / 33 ) * 33;
$blue = round( $blue / 33 ) * 33;

// convert decimal colors back to hexadecimal
$red = dechex( $red );
$green = dechex( $green );
$blue = dechex( $blue );

// concatenate colors back into hex string and add to array
$browserSafe[] = $red . $green . $blue;
}

?>

Obviously you could combine several of these steps and make the function shorter. I just wanted to give you a starting point that was easy to follow.

rayzun

I quess which color format has a lower color denominations.
YIKES is right!!!

with two character conversion, in my grey scale
465 combined .$vars

with six character 155

alimadzi

It also occurred to me that you might want to take my code and package it as a function. That would make it easier to run it once or twice if you wanted to or to use the code in other projects. You could also use the array_map() function to apply the function to each element of an input array in one line of code. Check it out...

http://www.php.net/manual/en/function.array-map.php

Let me know if you have any other questions.

alimadzi

Just realized that where I'm using 33 in my code, I should be using 51 (the decimal equivalent of hex 33). Sorry.