A processing method, applied to a mobile device, wherein the method comprises: receiving a photographing instruction; determining, through edge detection, four sides of a document image corresponding to a target document in a preview box of the mobile device; determining, based on the four sides, a first included angle corresponding to the document image, wherein the first included angle is used to represent an inclination degree of the document image relative to the target document, and the first included angle is positively correlated with an inclination angle of an image plane of a camera relative to the target document; if the first included angle is greater than a preset threshold, triggering the camera to reset a focus location in a direction of far-end content in the document image, and take n pictures, wherein n is an integer not less than 1; applying geometric correction to at least one of the n pictures obtained through photographing; and using, as output in response to the photographing instruction, one of the at least one picture to which geometric correction has been applied, wherein the determining, based on the four sides, a first included angle corresponding to the document image comprises: obtaining lengths of the four sides k 1, k 2, k 3, and k 4, wherein k 1 and k 3 are opposite sides, k 1 /k 3 ≥1, k 2 and k 4 are opposite sides, and k 2 /k 4 ≥1; calculating side ratios of the two pairs of opposite sides: k 1 /k 3 and k 2 /k 4; determining k 1 as a main side if k 1 /k 3 is greater than k 2 /k 4, or determining k 2 as a main side if k 2 /k 4 is greater than k 1 /k 3; and determining, as the first included angle, an included angle formed by intersection of two lateral sides of the main side, or the said determining comprises: obtaining lengths of the four sides k 1, k 2, k 3, and k 4, wherein k 1 and k 3 are opposite sides, and k 2 and k 4 are opposite sides; calculating a second included angle formed between the opposite sides k 1 and k 3 and a third included angle formed between the opposite sides k 2 and k 4; and determining, as the first included angle, the larger of the second included angle and the third included angle. receiving a photographing instruction; determining, through edge detection, four sides of a document image corresponding to a target document in a preview box of the mobile device; determining, based on the four sides, a first included angle corresponding to the document image, wherein the first included angle is used to represent an inclination degree of the document image relative to the target document, and the first included angle is positively correlated with an inclination angle of an image plane of a camera relative to the target document; if the first included angle is greater than a preset threshold, triggering the camera to reset a focus location in a direction of far-end content in the document image, and take n pictures, wherein n is an integer not less than 1; applying geometric correction to at least one of the n pictures obtained through photographing; and using, as output in response to the photographing instruction, one of the at least one picture to which geometric correction has been applied, wherein the determining, based on the four sides, a first included angle corresponding to the document image comprises: obtaining lengths of the four sides k 1, k 2, k 3, and k 4, wherein k 1 and k 3 are opposite sides, k 1 /k 3 ≥1, k 2 and k 4 are opposite sides, and k 2 /k 4 ≥1; calculating side ratios of the two pairs of opposite sides: k 1 /k 3 and k 2 /k 4; determining k 1 as a main side if k 1 /k 3 is greater than k 2 /k 4, or determining k 2 as a main side if k 2 /k 4 is greater than k 1 /k 3; and determining, as the first included angle, an included angle formed by intersection of two lateral sides of the main side, or the said determining comprises: obtaining lengths of the four sides k 1, k 2, k 3, and k 4, wherein k 1 and k 3 are opposite sides, and k 2 and k 4 are opposite sides; calculating a second included angle formed between the opposite sides k 1 and k 3 and a third included angle formed between the opposite sides k 2 and k 4; and determining, as the first included angle, the larger of the second included angle and the third included angle. obtaining lengths of the four sides k 1, k 2, k 3, and k 4, wherein k 1 and k 3 are opposite sides, k 1 /k 3 ≥1, k 2 and k 4 are opposite sides, and k 2 /k 4 ≥1; calculating side ratios of the two pairs of opposite sides: k 1 /k 3 and k 2 /k 4; determining k 1 as a main side if k 1 /k 3 is greater than k 2 /k 4, or determining k 2 as a main side if k 2 /k 4 is greater than k 1 /k 3; and determining, as the first included angle, an included angle formed by intersection of two lateral sides of the main side, or the said determining comprises: obtaining lengths of the four sides k 1, k 2, k 3, and k 4, wherein k 1 and k 3 are opposite sides, and k 2 and k 4 are opposite sides; calculating a second included angle formed between the opposite sides k 1 and k 3 and a third included angle formed between the opposite sides k 2 and k 4; and determining, as the first included angle, the larger of the second included angle and the third included angle. obtaining lengths of the four sides k 1, k 2, k 3, and k 4, wherein k 1 and k 3 are opposite sides, and k 2 and k 4 are opposite sides; calculating a second included angle formed between the opposite sides k 1 and k 3 and a third included angle formed between the opposite sides k 2 and k 4; and determining, as the first included angle, the larger of the second included angle and the third included angle.