Image encoding apparatus and method, image decoding apparatus and method, and storage medium

An image decoding apparatus that decodes, for each block, coded data generated by an image encoding apparatus that encodes image data for each block composed of a predetermined number of pixels, generates coded data having a preset target code size, and outputs the coded data, the apparatus comprising one or more processors and/or circuitry which function as:

• an acquisition unit that acquires image data;
• an encoding unit that encodes, for each block, the image data acquired by the acquisition unit such that a block code length of coded data for each block obtained through the encoding is equal to or less than the target code size;
• a determination unit that randomly determines priorities of the pixels constituting each block;
• and an addition unit that, in a case where the block code length of each block generated by the encoding unit is less than the target code size, adds to the coded data, in order from the pixel with a highest priority and without exceeding the target code size, a lost bit or bits of each pixel that were lost through the encoding, the image decoding apparatus comprising one or more processors and/or circuitry which function as:
• a second acquisition unit that acquires the coded data of each block;
• a decoding unit that decodes the coded data of each block acquired by the acquisition unit and generate decoded data;
• a determination unit that determines storage positions of the lost bit or bits in the coded data of each block, based on a result of decoding by the decoding unit;
• a determination unit that randomly determines priorities of the pixels constituting each block;
• and
• an addition unit that, based on the priorities determined by the determination unit, adds to the decoded data the lost bit or bits acquired from the storage positions determined by the determination unit, and outputs a result as pixel data.

An image encoding method that encodes image data for each block composed of a predetermined number of pixels, generates coded data having a preset target code size, and outputs the coded data, the method comprising:

• acquiring image data;
• encoding, for each block, the acquired image data such that a block code length of the coded data of each block obtained through the encoding is equal to or less than the target code size;
• randomly determining priorities of the pixels constituting each block;
• and
• in a case where the block code length of each block generated through the encoding is less than the target code size, adding, to the coded data, a lost bit or bits of each pixel that were lost through the encoding, in order from the pixel with a highest priority and without exceeding the target code size.

An image decoding method that decodes, for each block, coded data generated by an image encoding method that encodes image data for each block composed of a predetermined number of pixels, generates coded data having a preset target code size, and outputs the coded data, the method comprising:

• acquiring image data;
• encoding, for each block, the acquired image data such that a block code length of the coded data of each block obtained through the encoding is equal to or less than the target code size;
• randomly determining priorities of the pixels constituting each block;
• and in a case where the block code length of each block generated through the encoding is less than the target code size, adding, to the coded data, a lost bit or bits of each pixel that were lost through the encoding, in order from the pixel with a highest priority and without exceeding the target code size, the method comprising:
• acquiring the coded data of each block;
• decoding the acquired coded data of each block and generating decoded data;
• determining, based on a result of the decoding, storage positions of the lost bit or bits in the coded data of each block;
• randomly determining priorities of the pixels constituting each block;
• and
• adding, based on the determined priorities, to the decoded data, the lost bit or bits acquired from the determined storage positions, and outputting a result as pixel data.

A non-transitory computer-readable storage medium, the storage medium storing a program that is executable by the computer, wherein the program includes program code for causing the computer to function as an image encoding apparatus that encodes image data for each block composed of a predetermined number of pixels, generates coded data having a preset target code size, and outputs the coded data, the apparatus comprising:

• an acquisition unit that acquires image data;
• an encoding unit that encodes, for each block, the image data acquired by the acquisition unit such that a block code length of coded data for each block obtained through the encoding is equal to or less than the target code size;
• a determination unit that randomly determines priorities of the pixels constituting each block;
• and
• an addition unit that, in a case where the block code length of each block generated by the encoding unit is less than the target code size, adds to the coded data, a lost bit or bits of each pixel that were lost through the encoding, in order from the pixel with a highest priority and without exceeding the target code size.