How to stop GD2 from washing away the colors upon resizing images?

Question

I have developed a photo sharing community site using CodeIgniter 1.7. Photos that are uploaded by members are automatically resized in a number of formats, for which I use

Answer 1

I've managed to further test this with Imagick:

The left half of the image was processed with Imagick and the sRGB_IEC61966-2-1_no_black_scaling.icc color profile, the right half has no color profile associated and shows exactly the same if processed with Imagick or GD; here is the code I used:

header('Content-type: image/jpeg');

$image = new Imagick('/path/to/DSC07275.jpg');

if (($srgb = file_get_contents('http://www.color.org/sRGB_IEC61966-2-1_no_black_scaling.icc')) !== false)
{
    $image->profileImage('icc', $srgb);
    $image->setImageColorSpace(Imagick::COLORSPACE_SRGB);
}

$image->thumbnailImage(1024, 0);

echo $image;

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Here is a comparison of the several sRGB profiles available on the color.org website:

It seems to me that the third profile produces the most vivid results, other than that I have no idea how one would make a definitive choice.

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EDIT: Apparently, Imagick comes with a bundled sRGB profile, so you don't need to download the one from the Image Color Consortium website, the following code should handle all scenarios:

header('Content-type: image/jpeg');

$image = new Imagick('/path/to/DSC07275.jpg');
$version = $image->getVersion();
$profile = 'http://www.color.org/sRGB_IEC61966-2-1_no_black_scaling.icc';

if ((is_array($version) === true) && (array_key_exists('versionString', $version) === true))
{
    $version = preg_replace('~ImageMagick ([^-]*).*~', '$1', $version['versionString']);

    if (is_file(sprintf('/usr/share/ImageMagick-%s/config/sRGB.icm', $version)) === true)
    {
        $profile = sprintf('/usr/share/ImageMagick-%s/config/sRGB.icm', $version);
    }
}

if (($srgb = file_get_contents($profile)) !== false)
{
    $image->profileImage('icc', $srgb);
    $image->setImageColorSpace(Imagick::COLORSPACE_SRGB);
}

$image->thumbnailImage(1024, 0);

echo $image;