Colori RGB

di

Si assegnano 6 cifre esadecimali e si ottiene il codice, #RRGGBB, da utilizzare nelle pagine HTML

  1. Le cifre in base 16 sono: 0 1 2 3 4 5 6 7 8 9 A B C D E F
  2. In ogni coppia di cifre la prima cifra pesa più della seconda…
  3. Il codice per ogni componente del colore va da 00 a FF (da 0 a 255)
  4. Le combinazioni totali sono 16*16*16*16*16*16 = 224 (più di 16 milioni).

RGB
Red
Green
Blue 

<script language="JavaScript">
    var rgb16=Array("0", "1", "2", "3", "4", "5", "6", "7", "8", "9", 
                    "A", "B", "C", "D", "E", "F");
    function opzioni16()
    {
        for(i=0; i < 15; i++)
            document.writeln("<option value='" + rgb16[i] + "'>"+rgb16[i]+"</option>");
        document.writeln("<option value=" + rgb16[15] + " selected>"+rgb16[15]+"</option>");
    }
    function cambiaRgb()
    {
        var r1=document.colorergb.selectR1.value;   
        var r2=document.colorergb.selectR2.value;
        document.colorergb.coloreR.style.background="#"+r1+r2+"0000";   
        var g1=document.colorergb.selectG1.value;
        var g2=document.colorergb.selectG2.value;
        document.colorergb.coloreG.style.background="#00"+g1+g2+"00";       
        var b1=document.colorergb.selectB1.value;
        var b2=document.colorergb.selectB2.value;                  
        document.colorergb.coloreB.style.background="#0000"+b1+b2;
        var colore="#"+r1+r2+g1+g2+b1+b2;
        document.colorergb.colore.style.background=colore;
        document.colorergb.txtColore.value=colore;
    }
</script>
<form name="colorergb">
    <table cellspacing="0" cellpadding="3">
        <tr height=50>
            <td>RGB</td>
            <td><input type="text" value=" " name="colore" size="30" readonly /></td>
            <td><input type="text" value="#FFFFFF" name="txtColore" size="10" readonly /></td>
        </tr>
        <tr>
            <td>Red</td>
            <td><input type="text" value=" "  name="coloreR" size="30" readonly /></td>
            <td>
                <select name="selectR1" onChange="cambiaRgb();" ><script>opzioni16();</script></select> 
                <select name="selectR2" onChange="cambiaRgb();" ><script>opzioni16();</script></select>
            </td>
        </tr>
        <tr>
            <td>Green</td>
            <td><input type="text" value=" " name="coloreG" size="30" readonly /></td>
            <td>
                <select name="selectG1" onChange="cambiaRgb();" ><script>opzioni16();</script></select> 
                <select name="selectG2" onChange="cambiaRgb();" ><script>opzioni16();</script></select>
            </td>
        </tr>
        <tr>
            <td>Blue</td>
            <td><input type="text"   value=" "       name="coloreB" size="30" readonly /></td>
            <td>
                <select name="selectB1" onChange="cambiaRgb();" ><script>opzioni16();</script></select> 
                <select name="selectB2" onChange="cambiaRgb();" ><script>opzioni16();</script></select>
            </td>
        </tr>
    </table>
</form>
<script language="JavaScript">
    cambiaRgb();
</script>