1. An image evaluation method for a digital camera, the image evaluation method comprising: performing an image evaluation process on an image received with the digital camera, the image evaluation process for the image comprising: analyzing the composition of an image for obtaining a characteristic of the composition of the image; computing an ideal characteristic value, a real characteristic value, and a difference value between the ideal characteristic value and the real characteristic value; and generating a grade according to the difference value to show quality related to the composition of the image; outputting the image and the grade; capturing the image; performing the image evaluation process on the captured image, for generating a post-evaluation grade related to quality of the composition of the captured image; and displaying the post-evaluation grade.