A method, performed by an image-processing device (110, 600), for evaluating alignment of a first stream of images from a first image sensor and a second stream of images from a second image sensor, wherein the first and second image sensors (301a, 301b) have overlapping fields of view, wherein the method comprises: aligning a first image frame of the first stream of images and a further first image frame of the second stream of images according to a first alignment, aligning a second image frame of the first stream of images and a further second image frame of the second stream of images according to the first alignment, obtaining a first stitched image frame by blending the aligned first image frame and further first image frame in a first blending area of the first and further first image frames (311a, 311b) according to a first blending function, obtaining a second stitched image frame by blending the aligned second image frame and the further second image frame in a second blending area of the second and further second image frames (312a, 312b) according to a second blending function, and wherein the method is characterized in: evaluating the first alignment based on a difference pattern calculated based on values of corresponding pixels of the first stitched frame and the second stitched frame, wherein the corresponding pixels are comprised within at least one static part of the first and second blending areas (331a, 331b) in the respective first and second stitched image frames (321, 322), and wherein the method is further characterized in that: the second blending function differs from the first blending function, and the first blending function defines a respective blending weight of the aligned first image frame and the further first image frame as a function of a pixel position in the first blending area, and the second blending function defines a respective blending weight of the aligned second image frame and the further second image frame as a function of a pixel position in the second blending area. aligning a first image frame of the first stream of images and a further first image frame of the second stream of images according to a first alignment, aligning a second image frame of the first stream of images and a further second image frame of the second stream of images according to the first alignment, obtaining a first stitched image frame by blending the aligned first image frame and further first image frame in a first blending area of the first and further first image frames (311a, 311b) according to a first blending function, obtaining a second stitched image frame by blending the aligned second image frame and the further second image frame in a second blending area of the second and further second image frames (312a, 312b) according to a second blending function, and wherein the method is characterized in: evaluating the first alignment based on a difference pattern calculated based on values of corresponding pixels of the first stitched frame and the second stitched frame, wherein the corresponding pixels are comprised within at least one static part of the first and second blending areas (331a, 331b) in the respective first and second stitched image frames (321, 322), and wherein the method is further characterized in that: the second blending function differs from the first blending function, and the first blending function defines a respective blending weight of the aligned first image frame and the further first image frame as a function of a pixel position in the first blending area, and the second blending function defines a respective blending weight of the aligned second image frame and the further second image frame as a function of a pixel position in the second blending area. the second blending function differs from the first blending function, and the first blending function defines a respective blending weight of the aligned first image frame and the further first image frame as a function of a pixel position in the first blending area, and the second blending function defines a respective blending weight of the aligned second image frame and the further second image frame as a function of a pixel position in the second blending area.