| 摘要 |
PURPOSE:To effectively utilize a space part after updating by utilizing, when the space part is generated in the updating time of a picture data within a picture memory, the space part to save the picture data before updating. CONSTITUTION:An image A (A1 represents the bit plane of LSB, and Ar that of MSB) having gradation of n-number of bits has already been stored at a picture memory 21. In such a state, when an image B having gradation of k (k<n)-number of bits is stored at the picture memory 21 in a bit plane unit, (n-k)-number of bite planes are generated as the space. The capacity of the space part is calculated from the data quantity of the image to be updated, and the storage capacity of the picture memory by a CPU. And the picture data from the bit plane An to the bit plane Ak+1 of the MSB in the image A stored on the picture memory before updating are saved at the (n-k)-number of bit planes generated at the picture memory 21 after updating.
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