public byte[] extractMaxImage(bool NoOutput, string archiveDir = null, string fileName = null)
{
// select max image size, excluding void images with offset = -1
ImageSize maxImgSize = privateimgList.Where(img => img.offset != -1).Max(image => image.imgSize);
// extracting max image
return extractImage(privateimgList.Find(img => img.imgSize == maxImgSize), NoOutput, archiveDir, fileName);
}