C++ Converting color value String to int

Question

I have tried to convert a color code by reading a file, retrieve the color code and store it as a string. This works, but when I tried to just simply convert it to an int, it doesn't work - always getting 0 when I do a cout.

string value = "0xFFFFFF";
unsigned int colorValue = atoi(value.c_str());
cout << colorValue << endl;

as you can see, the color I've got is 0xFFFFFF, but converting it to an int will only give me 0. Can someone please tell me what I'm missing or what i'm doing wrong?

Thanks

`atoi` is C not C++ way. Also I believe `atoi` can't handle hex variables. — Bartek Banachewicz, Mar 31 '13 at 18:48
http://stackoverflow.com/questions/1070497/c-convert-hex-string-to-signed-integer — Daniel, Mar 31 '13 at 18:50
@DrewDormann sorry, I've posted my comment before I notice Daniel made a comment — Danny, Mar 31 '13 at 18:53

score 2 · Accepted Answer · answered Mar 31 '13 at 18:52

2

I suggest using stringstreams:

std::string value = "0xFFFFFF";
unsigned int colorValue;
std::stringstream sstream;
sstream << std::hex << value;
sstream >> colorValue;
cout << colorValue << endl;

answered Mar 31 '13 at 18:52

jwueller

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amrith92 · Answer 2 · 2013-03-31T19:00:41.410

0

As @BartekBanachewicz says, atoi() is NOT the C++ way of doing this. Leverage the power of C++ streams and use std::istringstream to do it for you. See this.

An excerpt:

template <typename DataType>
DataType convertFromString(std::string MyString)
{
    DataType retValue;
    std::stringstream stream;
    stream << std::hex << MyString; // Credit to @elusive :)
    stream >> retValue;
    return retValue;
}

edited Mar 31 '13 at 19:00

answered Mar 31 '13 at 18:53

amrith92

220
4
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That's a good idea, but the code as written will still produce the same problem. `"0xFFFFFF"` will return `0`. – Drew Dormann Mar 31 '13 at 18:57
Yes, just realized that. The solution is trivial, use @elusive's strategy. I'll update my answer :) – amrith92 Mar 31 '13 at 18:58

C++ Converting color value String to int

2 Answers2