Decoding device, program, and decoding method

A decoding device that performs a decoding process for a block obtained by dividing an original image including a plurality of color components, the decoding device comprising:

• an entropy decoder configured to decode a bitstream and thereby output
• transform coefficients being for each color component of the block,
• a first flag indicating for each color component whether the block includes a non-zero transform coefficient, and
• a second flag indicating whether a prediction residual transform process is applied to the block, the prediction residual transform process being a process generating a new prediction residual for each color component by a process using prediction residuals of two or more color components;
• an inverse quantizer/inverse transformer configured to restore the prediction residual from the transform coefficients for each color component;
• a prediction residual transformer configured to perform the prediction residual transform process for the prediction residual, when the second flag indicates that the prediction residual transform process is applied to the block;
• and
• a scaler configured to perform chroma residual scaling that performs scaling the prediction residual of a chrominance component based on a luminance component corresponding to the chrominance component, wherein
• the scaler is configured to determine whether to perform the chroma residual scaling based on the first flag of the color component and the second flag.