Abstract: An image processing apparatus has an original read unit for reading an image on an original document by a prescan and a copy scan, an image data processing unit for converting original image signals into digital image data signals and for processing the digital image data signals, and an output unit for outputting processed image data. The image processing apparatus further comprises an original detecting unit (3) for reading coordinates data on the original in a prescan mode, and enlargement/reduction processing units (2, 4 to 9) which store the image data read in a copy scan mode into a memory, execute the enlargement/reduction in accordance with the stored image data, whereby the enlargement/reduction processing units (2, 4 to 9) carry out the frame-erasure process by using the original coordinates data.

Abstract: A ground detection means 10 for detecting the ground level of a document and a data correction means 11 for calculating correction data based on the detected ground level are provided. The ground level of the document is detected by prescanning and the correction data is calculated therefrom so that parameters of color conversion means 2, 3 are changed by the correction data. The correction data is set by approximating the detected ground level with a linear function. As a result of the above construction, the correction data is generated easily to thereby remove ground fog and exclude back-side images of the document. In addition, if the ground level is detected by a lightness signal L* and corrected by the lightness signal L* or a color-separated signal BGR, the correction can be achieved by correcting the parameters of a matrix that converts the color-separated signals B, G, R to a system value (L*a*b*) signal.