Image encoding apparatus, method, and computer-readable storage medium for encoding a pixel value

An image encoding method performed by an image encoding apparatus that includes a central processing unit coupled to a memory unit storing a computer-executable program for encoding a pixel value, the method comprising:

• an inputting step of inputting, in a predetermined scan order, an image to be encoded:
• a first encoding step of encoding a pixel value of a target pixel using a pixel value of a pixel encoded precedent to the target pixel;
• a second encoding step of counting, as a run, a number of pixels having the same value based on an original value, terminating the count and outputting encoded data based on the counted run if the target pixel is a run-ending pixel;
• and
• a switching step of switching between encoding in the first encoding step and encoding in the second encoding step,
• wherein said switching causes, after said second encoding outputs encoded data, said first encoding to start encoding the target pixel determined as the run-ending pixel, and
• wherein, when said switching switches from said second encoding unit to said first encoding, the target pixel is determined as the run-ending pixel, and said first encoding encodes the target pixel using a value of a pixel determined as the run-ending pixel other than the target pixel having a different value from an adjacent pixel.

An image encoding apparatus which encodes a pixel value, comprising:

• an input unit that inputs, in a predetermined scan order, an image to be encoded:
• a first encoding that encodes a pixel value of a target pixel using a pixel value of a pixel encoded precedent to the target pixel;
• a second encoding unit that counts, as a run, a number of pixels having the same value based on an original value, terminates and outputs encoded data based on the counted run if the target pixel is a run-ending pixel having a different value from an adjacent pixel;
• and
• a switching unit that switches between encoding by said first encoding unit and encoding by said second encoding unit,
• wherein said switching unit causes, after said second encoding unit outputs encoded data, said first encoding unit to start encoding the target pixel determined as the run-ending pixel, and
• wherein, when said switching unit switches from said second encoding unit to said first encoding unit, the target pixel is determined as the run-ending pixel, and said first encoding unit encodes the target pixel using a value of a pixel immediately before the start pixel of the run immediately before the target pixel.

An image encoding method performed by an image encoding apparatus that includes a central processing unit coupled to a memory unit storing a computer-executable program for encoding a pixel value, the method comprising:

• an inputting step of inputting, in a predetermined scan order, an image to be encoded:
• a first encoding step of encoding a pixel value of a target pixel using a pixel value of a pixel encoded precedent to the target pixel;
• a second encoding step of counting, as a run, a number of pixels having the same value based on an original value, and outputting encoded data based on the counted run if the target pixel is a run-ending pixel having a different value from an adjacent pixel;
• and
• a switching step of switching between encoding in the first encoding step and encoding in the second encoding step,
• wherein said switching causes, after said outputting of the encoded data, encoding the target pixel determined as the run-ending pixel, and
• wherein, when said switching switches from said second encoding to said first encoding, the target pixel is determined as the run-ending pixel, and said first encoding encodes the target pixel using a value of a pixel immediately before the start pixel of the run immediately before the target pixel.