Image synthesizing apparatus for superposing a second image on a first image

DETAILED DESCRIPTION It is therefore an object of the present invention to solve the problems in the prior art.
It is another object of the present invention to provide an apparatus which is relatively small in scale and inexpensive in cost but which can perform high-speed mask synthesis conveniently.
In order to attain the above objects, according to the present invention, the image synthesizing apparatus for synthesizing first and second images with each other comprises: a first display memory for storing a first image data constituting a first image; and a display memory control means for comparing a second image data for constituting a second image with a predetermined image data to thereby judge whether the second image data is to be written into the first display memory or not.
For example, the above-mentioned unit image data is a pixel data.
The display memory control means may be constituted by a first comparison means for comparing the second image data at every unit image data with the predetermined image data, and a write control means for controlling writing of the second image data into the second display memory on the basis of the result of comparison of the first comparison means.
The above-mentioned predetermined image data has a specific range so that the first comparison means outputs a coincidence signal when the second image data is included within the range, and the write control means inhibits writing in the second display memory in response to the coincidence signal.
Although the second image data may be stored in a main memory, it may be stored in the second display memory provided separately.
In the case where the second display memory is provided, the display memory control means may further include a display reading means for reading image data periodically from the first and second display memories to display the image data, a second comparison means for comparing the second image data read from the second display memory at every unit image data with the predetermined image data, and a selection means for selecting one of the first and second image data read from the first and second display memories on the basis of the result of comparison of the second comparison means