Method and apparatus for encoding image by using quantization table adaptive to image

An apparatus for encoding an image, the apparatus comprising:

• at least one memory storing a machine learning model, trained to output a quantization table, and at least one instruction;
• and
• at least one processor configured to execute the at least one instruction to:
• obtain a plurality of patches from the image;
• obtain a plurality of transform coefficient groups respectively corresponding to the plurality of patches;
• input, to the machine learning model, input values corresponding to transform coefficients comprised in each of the plurality of transform coefficient groups;
• quantize transform coefficients corresponding to the image by using the quantization table output from the machine learning model;
• and
• generate a bitstream comprising data generated as a result of the quantizing and information about the quantization table.