GD Thumbnails turning black

[Sayian]

Hi all

Im using a thumnailing function as follows

function image_createThumb($src,$dest,$maxWidth,$maxHeight,$quality=100) {
    if (file_exists($src)  && isset($dest)) {
        // path info
        $destInfo  = pathInfo($dest);

    // image src size
    $srcSize   = getImageSize($src);

    // image dest size $destSize[0] = width, $destSize[1] = height
    $srcRatio  = $srcSize[0]/$srcSize[1]; // width/height ratio
    $destRatio = $maxWidth/$maxHeight;
    if ($destRatio > $srcRatio) {
        $destSize[1] = $maxHeight;
        $destSize[0] = $maxHeight*$srcRatio;
    }
    else {
        $destSize[0] = $maxWidth;
        $destSize[1] = $maxWidth/$srcRatio;
    }

    // true color image, with anti-aliasing
    $destImage = imageCreateTrueColor($destSize[0],$destSize[1]);
    imageAntiAlias($destImage,true);

    // src image
    switch ($srcSize[2]) {
        case 1: //GIF
        $srcImage = imageCreateFromGif($src);
        break;

        case 2: //JPEG
        $srcImage = imageCreateFromJpeg($src);
        break;

        case 3: //PNG
        $srcImage = imageCreateFromPng($src);
        break;

        default:
        return false;
        break;
    }

    // resampling
    imageCopyResampled($destImage, $srcImage, 0, 0, 0, 0,$destSize[0],$destSize[1],$srcSize[0],$srcSize[1]);

    // generating image
    switch ($srcSize[2]) {
        case 1:
        imageGif($destImage,$dest);
        break;
        case 2:
        imageJpeg($destImage,$dest,$quality);
        break;
        case 3:
        imagePng($destImage,$dest);
        break;
    }
    return true;
}
else {
    return false;
}
} 

The problem is, on some images, esp. low quality ones like camera phone pics, ect it's turning the thumbnail black

Anyone know why this could be occuring?