Image processing apparatus, method, and program

1. An image processing apparatus comprising:

a tone mapper that losslessly tone maps image data in a floating-point representation with a lossless logarithmic mapping by multiplying a differential value between an exponent of the image data in a floating-point representation and a minimum value of the exponent by 2 to a power of a bit depth of a mantissa of the image data in a floating-point representation, and further adds the mantissa of the image data in a floating-point representation to a result of the multiplication;

a base layer generator that generates base layer image data by reducing the bit depth of the image data tone mapped by the tone mapper; and

an enhancement layer generator that generates enhancement layer data by using the image data tone mapped by the tone mapper and the base layer image data generated by the base layer generator.

2. The image processing apparatus according to claim 1 , wherein the base layer generator includes

a first computing unit that subjects the image data tone mapped by the tone mapper to calculation by 2 to a power of a negative of an absolute value of the bit depth of the base layer image data, and

a rounding unit that generates the base layer image data by discarding a fractional part of the image data subjected to the power of 2 multiplication by the first computing unit.

3. The image processing apparatus according to claim 2 , wherein

the first computing unit bitshifts a pixel value in the image data tone mapped by the tone mapper to a right by an amount equivalent to the bit depth of the base layer image data.

4. The image processing apparatus according to claim 2 , wherein the enhancement layer generator includes

a second computing unit that subjects the base layer image data to calculation by 2 to a power of the bit depth of the base layer image data, and

a differential data generator that generates differential data between the image data tone mapped by the tone mapper and the base layer image data subjected to the power of 2 calculation by the second computing unit.

5. The image processing apparatus according to claim 4 , wherein

the second computing unit bitshifts a pixel value in the base layer image data to a left by an amount equivalent to the bit depth of the base layer image data.

6. The image processing apparatus according to claim 1 , further comprising:

a base layer encoder that encodes the base layer image data generated by the base layer generator.

7. The image processing apparatus according to claim 1 , further comprising:

an enhancement layer encoder that encodes the enhancement layer data generated by the enhancement layer generator.

8. An image processing method for an image processing apparatus, the image processing apparatus

losslessly tone mapping image data in a floating-point representation with a lossless logarithmic mapping by multiplying a differential value between an exponent of the image data in a floating-point representation and a minimum value of the exponent by 2 to a power of a bit depth of a mantissa of the image data in a floating-point representation, and further adds the mantissa of the image data in a floating-point representation to a result of the multiplication,

generating base layer image data by reducing a bit depth of the tone mapped image data,

generating enhancement layer data by using the tone mapped image data and the generated base layer image data.

9. A non-transitory computer-readable medium on which is recorded a program for causing a computer to function as:

a tone mapper that losslessly tone maps image data in a floating-point representation with a lossless logarithmic mapping by multiplying a differential value between an exponent of the image data in a floating-point representation and a minimum value of the exponent by 2 to a power of a bit depth of a mantissa of the image data in a floating-point representation, and further adds the mantissa of the image data in a floating-point representation to a result of the multiplication;

a base layer generator that generates base layer image data by reducing a bit depth of the image data tone mapped by the tone mapper; and

an enhancement layer generator that generates enhancement layer data by using the image data tone mapped by the tone mapper and the base layer image data generated by the base layer generator.