Apparatus for substituting character data for image data using orthogonal conversion coefficients

A character font combining apparatus for substituting character data for image data, comprising:

• means for storing compressed image data, said compressed image data being obtained by dividing digital original image data into a plurality of blocks, performing an orthogonal conversion, and encoding said data for each block;
• decoding means for decoding image data read out from said image data storing means and means for determining an orthogonal conversion coefficient for each block;
• character data storage means for storing a character font comprising at least an orthogonal conversion coefficient of one block;
• encoding means for encoding said orthogonal conversion coefficient for each block to obtain encoded data and, at the same, for writing said encoded data in said image data storing means;
• and
• substitution means for substituting at least one said orthogonal conversion coefficients determined by said decoding means with said orthogonal conversion coefficient stored in said character data storage means and, at the same time, for writing said substituted orthogonal conversion coefficient to said encoding means.