* @param string $extName Extension to differenciate thumb file name ('_small', '_mini')
* @param string $extName Extension to differenciate thumb file name ('_small', '_mini')
* @param int $quality Quality of compression (0=worst, 100=best)
* @param int $quality Quality of compression (0=worst, 100=best)
* @param string $outdir Directory where to store thumb
* @param string $outdir Directory where to store thumb
* @param int $targetformat New format of target (1,2,3,... or 0 to keep old format)
* @param int $targetformat New format of target (IMAGETYPE_GIF, IMAGETYPE_JPG, IMAGETYPE_PNG, IMAGETYPE_BMP, IMAGETYPE_WBMP ... or 0 to keep old format)
* @return string Full path of thumb or '' if it fails
* @return string Full path of thumb or '' if it fails