the invention provides a method of generating a scan image having cmy color information , in addition to a scan image having rgbcolor information , by forming three mixed light sources by turning on two of the three light sources sequentially and illuminating a scan target by the three mixed light sources sequentially . to preview the scan target , the scanner outputs the scan image having rgb color information . to print the scan target , the scanner outputs the scan image having cmy color information . fig1 is a schematic diagram of an embodiment of a scanner 101 . the scanner 101 includes three light sources 102 of different colors and an image capture unit 103 . the three light sources 102 are a red light source 102 a , a green light source 102 b , and a blue light source 102 c respectively . the image capture unit 103 is a contact image sensor ( cis ), scanning a scan target disposed on the scanner 101 . fig2 is a flowchart of an embodiment of a scanning method with light mixing . first , in step s 11 , the scan target is disposed on the scanner 101 . in step s 12 , two light sources are selected from the three light sources 102 according to requirements . in this embodiment , the red light source 102 a and the green light source 102 b are selected . in step s 13 , the two selected light sources are turned on simultaneously to form a mixed light source . in this embodiment , the mixed light source formed by turning on the red light source 102 a and the green light source 102 b simultaneously is a yellow light source . additionally , in this step , the scan target is illuminated by the mixed light source . finally , in step s 14 , the image capture unit 103 scans the scan target to generate an image signal . in this embodiment , the image signal generated is an image signal from which yellow color is filtered out . fig3 is a schematic diagram of another embodiment of a scanner 201 , wherein the scanner 201 is connected to a printer 204 in a computer system . the scanner 201 includes three light sources 202 of different colors and an image capture unit 103 . the scanner 201 is connected to the printer 204 in the computer system . the three light sources 202 are a first light source 202 a , a second light source 202 b , and a third light source 202 c respectively . in this embodiment , the first light source 202 a is red , the second light source 202 b is green , and the third light source 202 c is blue . the image capture unit 203 is a contact image sensor ( cis ), scanning a scan target disposed on the scanner 201 . fig4 is a flowchart of another embodiment of a scanning method with light mixing . first , in step s 21 , the scan target is disposed on the scanner 201 . in step s 22 , the first light source 202 a and the second light source 202 b are turned on simultaneously to form a first mixed light source . in this embodiment , the first mixed light source formed by turning on the red light source 202 a and the green light source 202 b simultaneously is a yellow light source . additionally , in this step , the scan target is illuminated by the first mixed light source . in step s 23 , the image capture unit 203 scans the scan target to generate a first image signal . in step s 24 , the second light source 202 b and the third light source 202 c are turned on simultaneously to form a second mixed light source . in this embodiment , the second mixed light source formed by turning on the green light source 202 b and the blue light source 202 c simultaneously is a cyan light source . additionally , in this step , the scan target is illuminated by the second mixed light source . in step s 25 , the image capture unit 203 scans the scan target to generate a second image signal . in step s 26 , the third light source 202 c and the first light source 202 a are turned on simultaneously to form a third mixed light source . in this embodiment , the third mixed light source formed by turning on the blue light source 202 c and the red light source 202 a simultaneously is a magenta light source . additionally , in this step , the scan target is illuminated by the third mixed light source . in step s 27 , the image capture unit 203 scans the scan target to generate a third image signal . in step s 28 , the first , the second , and the third image signals are combined to form a scan image having cmy color information , i . e . cyan , magenta , yellow color information . finally , in step s 29 , the scan image is output to the printer 204 directly . it is noted that because the printer 204 can process a cmy image directly , the scan image can be input to the printer 204 directly without any transformation or processing . fig5 is a schematic diagram of another embodiment of a scanner 301 , wherein the scanner 301 is connected to a printer 304 and a display 305 in a computer system . the scanner 301 includes three light sources 302 of different colors and an image capture unit 303 . the scanner 301 is connected to the printer 304 and the display 305 in the computer system . the three light sources 302 are a red light source 302 a , a green light source 302 b , and a blue light source 302 c respectively . the image capture unit 303 is a contact image sensor ( cis ), scanning a scan target disposed on the scanner 301 . fig6 is a flowchart of another embodiment of a scanning method with light mixing . first , in step s 31 , the scan target is disposed on the scanner 301 . in conditional step c 31 , an output mode of the scanner 301 is determined . if the output mode is “ preview ”, the process goes to step s 32 . in step s 32 , the three light sources 302 a , 302 b , 302 c are turned on sequentially to illuminate the scan target . next , in step s 33 , the image capture unit 303 scans the scan target to generate a first scan image . finally , in step s 34 , the first scan image is output to the display 305 after which the process stops . if the output mode is “ print ”, the process goes to step s 35 . in step s 35 , two of the three light sources 302 a , 302 b , 302 c are turned on sequentially to form three mixed light sources . in this embodiment , the three mixed light sources formed are yellow , cyan , and magenta light sources respectively . additionally , in this step , the scan target is illuminated by the three mixed light sources sequentially . next , in step s 36 , the image capture unit 303 scans the scan target to generate a second scan image . finally , in step s 37 , the second scan image is output to the printer 304 after which the process stops . some embodiments of a scanning method with light mixing can generate a scan image having cmy color information , in addition to a scan image having rgb color information , by forming three mixed light sources by turning on two of the three light sources sequentially and illuminating a scan target by the three mixed light sources sequentially . to preview the scan target , the scanner outputs the scan image having rgb color information , and to print the scan target , the scanner outputs the scan image having cmy color information , thus avoiding loss of color information and waste of time due to color format transformation . while the invention has been described by way of example and in terms of preferred embodiments , it is to be understood that the invention is not limited thereto . to the contrary , it is intended to cover various modifications and similar arrangements ( as would be apparent to those skilled in the art ). therefore , the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements .