Image re-encoding method and device thereof

A method of determining whether an image is to be re-encoded, the method comprising:

• obtaining a first quantization matrix from an image file including the image, the image being encoded by quantization based on the first quantization matrix including a plurality of first quantization parameters;
• obtaining a second quantization matrix from a re-encoding device, the second quantization matrix including a plurality of second quantization parameters and having the same size as the first quantization matrix;
• determining a comparison coefficient corresponding to a cumulative value obtained by adding weights allocated to locations of the elements greater than ‘0’ among the elements of the comparison matrix to be the comparison coefficient;
• and
• when the comparison coefficient is greater than a first threshold value, determining that the image is to be decoded by inverse quantization based on the first quantization matrix and the decoded image is to be re-encoded by quantization based on the second quantization matrix.

A device for determining whether an image is to be re-encoded, the device comprising:

• a memory configured to store instructions;
• and
• a processor configured to execute the instructions, causing the processor to:
• obtain a first quantization matrix from an image file including the image, the image being encoded by quantization based on the first quantization matrix including a plurality of first quantization parameters,
• obtain a second quantization matrix from a re-encoding device, the second quantization matrix including a plurality of second quantization parameters and having the same size as the first quantization matrix,
• determine a comparison coefficient corresponding to a cumulative number of elements greater than ‘0’ in a comparison matrix obtained by subtracting the first quantization matrix from the second quantization matrix, and
• when the comparison coefficient is greater than a first threshold value, determine that the image is to be decoded by inverse quantization based on the first quantization matrix and the decoded image is to be re-encoded by quantization based on the second quantization matrix.

A device for determining whether an image is to be re-encoded, the device comprising:

• a memory configured to store instructions;
• a processor configured to execute the instructions, causing the processor to:
• obtain a first quantization matrix from an image file including the image, the image being encoded by quantization based on the first quantization matrix including a plurality of first quantization parameters,
• obtain a second quantization matrix from a re-encoding device, the second quantization matrix including a plurality of second quantization parameters and having the same size as the first quantization matrix,
• determine a comparison coefficient corresponding to a cumulative value obtained by adding weights allocated to locations of the elements greater than ‘0’ among the elements of the comparison matrix, and
• when the comparison coefficient is greater than a first threshold value, determine that the image is to be decoded by inverse quantization based on the first quantization matrix and the decoded image is to be re-encoded by quantization based on the second quantization matrix.