縮放圖片

+(UIImage *)scaleImage:(UIImage *)_image size:(CGSize)_size

{

    CGFloat _toWidth  = _size.width;

    CGFloat _toHeight = _size.height;

    float _x = 0.0f;

    float _y = 0.0f;

    CGRect _frame = CGRectMake(_x, _y, _toWidth, _toHeight);

    float _oldWidth  = _image.size.width;

    float _oldHeight = _image.size.height;

    float _scaleRatio   = MAX( (_toWidth / _oldWidth), (_toHeight / _oldHeight) );

    float _equalWidth   = (int)( _oldWidth * _scaleRatio );

    float _equalHeight  = (int)( _oldHeight * _scaleRatio );

    UIGraphicsBeginImageContext( CGSizeMake(_equalWidth, _equalHeight) );

    [_image drawInRect:CGRectMake(0, 0, _equalWidth, _equalHeight)];

    _image = nil;

    _image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    _x = floor( (_equalWidth -  _toWidth) / 2 );

    _y = floor( (_equalHeight - _toHeight) / 2 );

    _frame = CGRectMake(_x, _y, _toWidth, _toHeight);

    CGImageRef _smallImage = CGImageCreateWithImageInRect( [_image CGImage], _frame );

    UIImage *_doneImage    = [UIImage imageWithCGImage:_smallImage];

    CGImageRelease(_smallImage);

    return _doneImage;

}