Reducing grid line artifacts in an X-ray image II, comprising: acquiring an X-ray image II by scanning an object (200, Fig. 1), where the X-ray image comprises grid line artifacts； decomposing 3 the X-ray image into high Ihf and low Ilf frequency images, where the high frequency image comprises grid line artifacts； processing 4 the high frequency image to reduce grid line artifacts and produce filtered high frequency image Ifilt； combining 5 the processed high frequency image and low frequency image to generate an output image Io. High pass filter (31, Fig. 4) may be used to obtain high frequency image, and low frequency image may be obtained by subtracting (33, Fig. 4) high frequency image from X-ray image. Low pass filter (32, Fig. 5) may be used to obtain low frequency image, and high frequency image may be obtained by subtracting (33, Fig. 5) low frequency image from X-ray image. Filtering the high frequency image may comprise identifying strong edge in high frequency image. Filtering high frequency image may include performing Fourier Transform.
