Image encoding method and apparatus

An image processing method comprising:

• an encoding step, of dividing an image into blocks and performing variable-length encoding for the image;
• a storing step, of storing encoded data obtained in the encoding step into a memory;
• and
• a control step, of controlling a compression condition of the encoding step based on a result of comparing a preset code amount of an accumulated encoded area with an accumulated code amount, so that the amount of the encoded data falls within a predetermined range by a single encoding operation, said preset code amount having an allowable range,
• wherein a relation between an allowable range D1 of a preset code amount for an amount of processed code data K1 and an allowable range D2 of a preset code amount for an amount of processed code data K2 is D1>D2 when K1<K2.

An image data encoding apparatus comprising:

• an inputter for inputting data representing an image constituted by a plurality of block images, and for sequentially supplying image data representing individual ones of the plurality of block images, on a block by block basis;
• an image data transformer, arranged for transforming image data representing an individual block image, supplied by said inputter, into corresponding spatial frequency component data;
• an encoder, arranged for quantizing the spatial frequency component data supplied by said image data transformer, to provide quantized spatial frequency component data, and for encoding the quantized spatial frequency component data;
• a comparer, arranged for comparing an amount of encoded spatial frequency component data provided by said encoder with a predetermined lower value and a predetermined higher value, before said encoder encodes next spatial frequency component data;
• and
• a quantization parameter setter, arranged for setting a quantization parameter to be utilized by said encoder for quantizing the next spatial frequency component data, based on a comparison result of said comparer so that the amount of the encoded data falls within a predetermined range,
• wherein a relation between an allowable range D1 of a preset code amount for an amount of processed code data K1 and an allowable range D2 of a preset code amount for an amount of processed code data K2 is D1>D2 when K1<K2.

An image data encoding method comprising the steps of:

• an input step, of inputting data representing an image constituted by a plurality of block images, and sequentially supplying image data representing individual ones of the plurality of block images block, on a block by block basis;
• a transforming step, of transforming image data representing an individual block image, supplied in said input step, into corresponding spatial frequency component data;
• an encoding step, of quantizing the spatial frequency component data supplied in said transforming step, to provide quantized spatial frequency component data, and encoding the quantized spatial frequency component data;
• a comparing step, of comparing an amount of encoded spatial frequency component data provided in said encoding step with a predetermined lower value and a predetermined higher value, before next spatial frequency component data is encoded in said encoding step;
• and
• a setting step, of setting a quantization parameter to be utilized for quantizing the next spatial frequency component data in said encoding step, based on a comparison result of said comparing step so that the amount of the encoded data falls within a predetermined range,
• wherein a relation between an allowable range D1 of a preset code amount for an amount of processed code data K1 and an allowable range D2 of a preset code amount for an amount of processed code data K2 is D1>D2 when K1<K2.