Encoder, decoder, encoding method, decoding method, and recording medium

A decoder, comprising:

• an acquisition unit configured to acquire encoded RAW image data resulting from encoding gradation correction RAW image data that has undergone gradation correction on the basis of a gamma coefficient and an optical black value;
• a decoding unit configured to decode the encoded RAW image data acquired by the acquisition unit into the gradation correction RAW image data;
• and
• an inverse gradation correction unit configured to execute inverse gradation correction on the gradation correction RAW image data decoded by the decoding unit on the basis of the gamma coefficient and the optical black value, and output the RAW image data prior to gradation correction,
• wherein the inverse correction unit is configured to execute first inverse gradation correction for a first interval in which the input signal level of the gradation correction RAW image data is less than a prescribed value, and execute second inverse gradation correction for a second interval in which the input signal level of the RAW image data is in at least a portion of a range from the prescribed value to a maximum value.

An encoding method, comprising:

• a correction process of executing gradation correction on RAW image data from an image capture element having optical black on the basis of a gamma coefficient and an optical black value of the optical black;
• and
• an encoding process of encoding gradation correction RAW image data that has undergone gradation correction by the correction process,
• wherein the correction process executes first gradation correction for a first interval in which the input signal level of the RAW image data is less than the optical black value, and executes second gradation correction for a second interval in which the input signal level of the RAW image data is in at least a portion of a range from the optical black value to a maximum value.

A decoding method, comprising:

• an acquisition process of acquiring encoded RAW image data resulting from encoding gradation correction RAW image data that has undergone gradation correction on the basis of a gamma coefficient and an optical black value;
• a decoding process of decoding the encoded RAW image data acquired by the acquisition process into the gradation correction RAW image data;
• and
• an inverse gradation correction process of executing inverse gradation correction on the gradation correction RAW image data decoded by the decoding process on the basis of the gamma coefficient and the optical black value, and outputting the RAW image data prior to gradation correction;
• wherein the inverse correction process executes first inverse gradation correction for a first interval in which the input signal level of the gradation correction RAW image data is less than a prescribed value, and executes second inverse gradation correction for a second interval in which the input signal level of the RAW image data is in at least a portion of a range from the prescribed value to a maximum value.