Understanding colors on Android six characters

Question

I am trying to understand how colors work in Android  I have this color set as the background of my LinearLayout  and I get a background gray with some transparency    lt gradient android startColor   b4555555  android endColor   b4555555   android angle  270 0    gt    If I remove the last two characters  55  I get a solid color  losing the transparency  I was trying to find a page where I can see some explanation about this  but I couldn t find it

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On Android  colors are can be specified as RGB or ARGB   http   en wikipedia org wiki ARGB  In RGB you have two characters for every color  red  green  blue   and in ARGB you have two additional chars for the alpha channel   So  if you have 8 characters  it s ARGB  with the first two characters specifying the alpha channel  If you remove the leading two characters it s only RGB  solid colors  no alpha transparency   If you want to specify a color in your Java source code  you have to use   int Color argb  int alpha  int red  int green  int blue   alpha  Alpha component  0  255  of the color red    Red component  0  255  of the color green  Green component  0  255  of the color blue   Blue component  0  255  of the color   Reference  argb

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An 8-digit hex color value is a representation of ARGB  Alpha  Red  Green  Blue   whereas a 6-digit value just assumes 100  opacity  fully opaque  and defines just the RGB values  So to make this be fully opaque  you can either use  FF555555  or just  555555  Each 2-digit hex value is one byte  representing values from 0-255

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Android uses hexadecimal ARGB values  which are formatted as  AARRGGBB  That first pair of letters  the AA  represent the alpha channel  You must convert your decimal opacity values to a hexadecimal value  Here are the steps   Alpha Hex Value Process   Take your opacity as a decimal value and multiply it by 255  So  if you have a block that is 50  opaque the decimal value would be  5  For example   5 x 255   127 5 The fraction won t convert to hexadecimal  so you must round your number up or down to the nearest whole number  For example  127 5 rounds up to 128  55 25 rounds down to 55  Enter your decimal value in a decimal-to-hexadecimal converter  like http   www binaryhexconverter com decimal-to-hex-converter  and convert your values  If you only get back a single value  prefix it with a zero  For example  if you re trying to get 5  opacity and you re going through this process  you ll end up with the hexadecimal value of D  Add a zero in front of it so it appears as 0D    That s how you find the alpha channel value  I ve taken the liberty to put together a list of values for you  Enjoy   Hex Opacity Values   100      FF 95      F2 90      E6 85      D9 80      CC 75      BF 70      B3 65      A6 60      99 55      8C 50      80 45      73 40      66 35      59 30      4D 25      40 20      33 15      26 10      1A 5      0D 0      00

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at new chrome version  maybe 67 0 3396 62    CSS hex color can use this model display    eg   div    background-color  FF00FFcc      cc is opacity   but old chrome not support that mod

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Android Material Design These are the conversions for setting the text color opacity levels   100   FF 87   DE 70   B3 54   8A 50   80 38   61 12   1F  Dark text on light backgrounds   Primary text  DE000000 Secondary text  8A000000 Disabled text  hint text  and icons  61000000 Dividers  1F000000  White text on dark backgrounds   Primary text  FFFFFFFF Secondary text  B3FFFFFF Disabled text  hint text  and icons  80FFFFFF Dividers  1FFFFFFF  See also  Look up any percentage here

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If you provide 6 hex digits  that means RGB  2 hex digits for each value of red  green and blue    If you provide 8 hex digits  it s an ARGB  2 hex digits for each value of alpha  red  green and blue respectively    So by removing the final 55 you re changing from A B4  R 55  G 55  B 55  a mostly transparent grey   to R B4  G 55  B 55  a fully-non-transparent dusky pinky    See the  Color  documentation for the supported formats

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On Android the color can be declared in the following format  AARRGGBB  AA - is the bit that   s of most interest to us  it stands for alpha channel RR GG BB - red  green  amp  blue channels respectively Now in order to add transparency to our color we need to prepend it with hexadecimal value representing the alpha  transparency   For example if you want to set 80  transparency value to black color   000000  you need to prepend it with CC  as a result we end up with the following color resource  CC000000  You can read about it in more detail  on my blog https   androidexplained github io android ui 2020 10 12 hex-color-code-transparency html

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Going off the answer from  BlondeFurious  here is some Java code to get each hexadecimal value from 100  to 0  alpha   for  double i   1  i  gt   0  i -  0 01        i   Math round i   100    100 0d      int alpha    int  Math round i   255       String hex   Integer toHexString alpha  toUpperCase        if  hex length      1          hex    0    hex      int percent    int   i   100       System out println String format   d        s   percent  hex        Output   100      FF 99      FC 98      FA 97      F7 96      F5 95      F2 94      F0 93      ED 92      EB 91      E8 90      E6 89      E3 88      E0 87      DE 86      DB 85      D9 84      D6 83      D4 82      D1 81      CF 80      CC 79      C9 78      C7 77      C4 76      C2 75      BF 74      BD 73      BA 72      B8 71      B5 70      B3 69      B0 68      AD 67      AB 66      A8 65      A6 64      A3 63      A1 62      9E 61      9C 60      99 59      96 58      94 57      91 56      8F 55      8C 54      8A 53      87 52      85 51      82 50      80 49      7D 48      7A 47      78 46      75 45      73 44      70 43      6E 42      6B 41      69 40      66 39      63 38      61 37      5E 36      5C 35      59 34      57 33      54 32      52 31      4F 30      4D 29      4A 28      47 27      45 26      42 25      40 24      3D 23      3B 22      38 21      36 20      33 19      30 18      2E 17      2B 16      29 15      26 14      24 13      21 12      1F 11      1C 10      1A 9      17 8      14 7      12 6      0F 5      0D 4      0A 3      08 2      05 1      03 0      00     A JavaScript version is below    x000D   x000D  var text   document getElementById  text    x000D  for  var i   1  i  gt   0  i -  0 01    x000D      i   Math round i   100    100  x000D      var alpha   Math round i   255   x000D      var hex    alpha   0x10000  toString 16  substr -2  toUpperCase    x000D      var perc   Math round i   100   x000D      text innerHTML    perc              hex          alpha      lt  br gt    x000D    x000D   lt div id  text  gt  lt  div gt  x000D   x000D   x000D      You can also just Google  number to hex  where  number  is any value between 0 and 255

[android] Understanding colors on Android (six characters)

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