Image boundary detection devices and methods include processes. Processes include setting an image recording mode to a second recording mode. First and second recording modes utilize first and second density values, respectively. Second density values are less than corresponding first density values. Processes include reducing first density values to second density values when the second recording mode is set. Processes include setting an image boundary determination threshold to one of a first and second threshold value when a respective one of the first and second recording mode is set. The second threshold value is less than the first threshold value. Processes include calculating density gradient values based on one of the first and second density value when the respective one of the first and second recording mode is set. Processes include determining whether pixels are image boundaries using density gradient values and the image boundary determination threshold.