Patent ID: 8054507

Claim:
An image data luminance compensating method for use in a sheet-feeding scanning apparatus, said sheet-feeding scanning apparatus comprising a scan operating region, an image capturing module and a reference background strip, said image capturing module and said reference background strip are disposed on opposite sides of said scan operating region, said image data luminance compensating method comprising: sensing the luminance value of said reference background strip by said image capturing module, thereby obtaining a first reference luminance value B 1 ; capturing a first image data D 1 of a first document passing through said scan operating region by said image capturing module, and compensating said first image data D 1 with a first luminance gain G 1 ; sensing the luminance value of said reference background strip by said image capturing module, thereby obtaining a second reference luminance value B 2 ; calculating a first luminance difference ratio R 1 according to said first reference luminance value B 1 and said second reference luminance value B 2 is calculated, in which R 1 =|1−B 1 /B 2 |; capturing a second image data D 2 of a second document passing through said scan operating region by said image capturing module; and compensating said second image data D 2 with said first luminance gain G 1 if said first luminance difference ratio R 1 is smaller than a threshold value, or compensating said second image data D 2 with a second luminance gain G 2 if said first luminance difference ratio R 1 is greater than or equal to said threshold value, in which G 2 =G 1 ×B 1 /B 2 .