| 摘要 |
PURPOSE:To mask the peripheral part of an image in an optional shape accurately and to display an easy-to-see image on a screen by providing a memory for storing the area of the image and a circuit which controls an image signal according to the data in the memory and masks the image. CONSTITUTION:Horizontal synchronizing pulses HD of a color monitor 14 are counted by a counter 50 to detect the position of the current horizontal scanning line. A ROM 56 is stored with information indicating from which picture element each scanning line begins to display on a monitor and a ROM 56 is stored with information indicating to which picture element each scanning line displays on the monitor; and they are read out according to the output of the counter 50. Readout clock pulses CK of frame memories 46a, 46b, and 46c are counted by a counter 52 and comparators 58 and 60 compare mask data read out of the ROMs 54 and 56 with data indicating the current display picture element outputted from the counter 52, thereby setting or resetting an F/F circuit 62 with the comparison outputs. The F/F circuit 62 supplies its output signal to enable terminals E of D/A converters 48a, 48b, and 48c.
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