An image processing apparatus includes a region detection unit configured to detect from an image a region which is sandwiched between a pair of opposite lines and in which image formation is performed at a density lower than a predetermined density, a rendering unit configured to render a border of an inner portion inside the region sandwiched between the pair of opposite lines with a line having a density higher than the predetermined density, and an outputting unit configured to output an image in which the inner portion inside the region sandwiched between the pair of opposite lines is bordered by the border rendered by the rendering unit.