Dynamically Adjusting HTML RGB Colours

In this article I shall be presenting a method of changing the RGB colours used in HTML. The examples presented in this article related to a requirement to be able to adjust the colour to be illustrated in a <td>, to show a series of stripes getting either lighter or darker.

The first function shown is used to darken the colour. For a given colour and modifier value it will return a darker colour.

<%
function colourDarker(myColour, modifier)
    thisColour=""
    item1=""
    item2=""
    item3=""
    for i = 1 to 6 step 2
        item1=mid(replace(myColour, "#", ""), i, 2)
        item2=mid(modifier, i, 2)
        item1 = CInt("&h"&item1)
        item2 = CInt("&h"&item2)
        item3=(item1-item2)
        if item3<0 then
            item3=0
        end if
        item3=CSTR(HEX(item3))
        if Len(item3)=1 then item3="0"+item3
        thisColour=thisColour+CStr(item3)
    next
    colourDarker=replace(thisColour, "&H", "")
end function
%>

and finally a short piece of HTML to product some stripes:

<table width="100">
<%
    For i = 2 to 8 step 2
    showColour=colourDarker("eeeeee", cStr(i & "0" & i & "0" & i & "0"))
%>
<tr>
<td width="100" bgcolor="<%=showColour%>">&nbsp;</td>
</tr>
<%next 'i%>
</table>