Convert HTML colour codes to

[ae_jester]

I have this code that works in VB for converting an html colour string into a visual basic colour. How can I do the same thing in C??????

Keep in mind that RGB does not work in C so I would need an equivalent function for this also.

'Convert a colour represented in html colour format,
'to a long value recognizable by visual basic
Function HTMLToLong(sHTML As String) As Long
    Dim lR As Long, lB As Long, lG As Long
 
    lR = CInt(Val("&h" + Mid(sHTML, 2, 2)))
    lG = CInt(Val("&h" + Mid(sHTML, 4, 2)))
    lB = CInt(Val("&h" + Mid(sHTML, 6, 2)))
 
    HTMLToLong = RGB(lR, lG, lB)
End Function

[Sastraxi]

I don't know C, so this may only be valid in C++... hell, I'm not that good, so it may not be valid at all...

long int HTMLToLong(char* sHTML[]) {
    long int lR; long int lB; long int lG;
    
    lR = (int)...
    lG = (int)...
    lB = (int)...

    return lR + lG * 256 + lB * 65536;

} 

I'm not sure how to do those middle parts, so I'll let a 'guru' fill those out, sorry.

[Zaei]

There is an RGB macro availible.

#define RGB(r, g ,b)  ((DWORD) (((BYTE) (r) | \ 
    ((WORD) (g) << 8)) | \ 
    (((DWORD) (BYTE) (b)) << 16)))

From MSDN.

As for the hex code to int... this should work:

char hex_byte_string_to_byte(char* code)
{
 int val[i];

 for(int i = 0; i < 2; ++i) 
 {
  if((code[i] >= '0') && (code[i] <= '9'))
  {
   val[i] = code[i] - '0';
  }
  else
  {
   val[i] = code[i] - 'A' + 10;
  }
 }
 return val[0] << 4 + val[1];
}

Seems correct, but I didnt test it.

Z.

[Sastraxi]

As I was taking a walk today, I realised that C has bitshifts in it. D'oh! So I was going to let you know, but of course Zaei beat me to it

[CornedBee]

There goes: converts any #xxxxxx string to a COLORREF:

#include <string>
#include <sstream>

COLORREF ReadHtmlColor(const string& str)
{
  istringstream iss(str);
  iss.ignore(1);
  int r, g, b;
  iss >> setbase(16) >> r >> g >> b;
  return RGB(r, g, b);
}

Should work.

[CornedBee]

Note however that HTML colors can also be in the format #xxx, where each color component is represented by a single hex digit. It's equivalent to writing #x0x0x0. Here's a function that can read this too.

Oh, and I noticed my function won't work, here's a corrected and complete version.

#include <string>
#include <sstream>
#include <iomanip>
using namespace std;

COLORREF ReadHtmlColor(const string& str)
{
  istringstream iss;
  int r, g, b;
  if(str.length() == 4) {
    iss.str((str.substr(1,1)));
    iss >> setbase(16) >> r;
    r <<= 8;
    iss.str((str.substr(2,1)));
    iss >> setbase(16) >> g;
    g <<= 8;
    iss.str((str.substr(3,1)));
    iss >> setbase(16) >> b;
    b <<= 8;
  } else if(str.length() == 7) {
    iss.str((str.substr(1,2)));
    iss >> setbase(16) >> r;
    iss.str((str.substr(3,2)));
    iss >> setbase(16) >> g;
    iss.str((str.substr(5,2)));
    iss >> setbase(16) >> b;
  } else return 0;
  return RGB(r,g,b);
}

There's probably a more beautiful method.

[Zaei]

Originally posted by CornedBee
Should work.

I use this line all the time =).

My function does work (just tested it), except you need to change "int val[i]" to "int val[2]".

Z.