Image processing apparatus, image processing method, storage medium, and program
AssigneeCanon Kabushiki Kaisha
InventorHiroyuki Shinbata
Life of this patent
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Abstract
There are provided an image processing apparatus and method. In this apparatus and method, high-frequency components are converted by multiple-frequency transformation in accordance with tone conversion used to change the dynamic range, thereby obtaining a high-quality image. For example, an original image undergoes tone conversion on the basis of a tone conversion curve, and the converted image then undergoes discrete wavelet transformation. After that, subbands obtained by discrete wavelet transformation undergo a conversion process in correspondence with the slope of the tone conversion curve.
Claims9
An image processing apparatus comprising:
- a tone conversion unit arranged to execute tone conversion of an original image based on a tone conversion curve;
- a frequency transformation unit arranged to decompose the original image or an image generated by executing the tone conversion of the original image into coefficients for a plurality of high frequency bands and one low frequency band;
- a component conversion unit arranged to convert the coefficients of the plurality of high frequency bands by converting values of those coefficients based on a slope of the tone conversion curve;
- and
- an inverse frequency transformation unit arranged to generate an image based on the converted coefficients;
- wherein the component conversion unit sets threshold values each corresponding to respective one of the plurality of frequency bands and converts each coefficient, whose value is greater than the corresponding threshold value, with a predetermined conversion rate.
An image processing method comprising:
- a tone conversion unit arranged to execute tone conversion of an original image based on a tone conversion curve;
- a frequency transformation step of decomposing the original image, or an image generated by executing the tone conversion of the original image, into coefficients for a plurality of high frequency bands and one low frequency band;
- a component conversion step of converting the coefficients of the plurality of high frequency bands by converting values of those coefficients based on a slope of the tone conversion curve;
- and
- an inverse frequency transformation step of generating an image based on the converted coefficients;
- wherein the component conversion step includes setting threshold values each corresponding to a respective one of the plurality of frequency bands and converting each coefficient, whose value is greater than a corresponding threshold value, with a predetermined conversion rate.
A computer-readable medium encoded with a computer program for a method of processing an image, the method comprising:
- a tone conversion unit arranged to execute tone conversion of an original image based on a tone conversion curve;
- a frequency transformation step of decomposing the original image, or an image generated by executing the tone conversion of the original image, into coefficients for a plurality of high frequency bands and one low frequency band;
- a component conversion step of converting the coefficients of the plurality of high frequency bands by converting values of those coefficients based on a slope of the tone conversion curve;
- and
- an inverse frequency transformation step of generating an image based on the converted coefficients;
- wherein the component conversion step includes setting threshold values each corresponding to a respective one of the plurality of frequency bands and converting each coefficient, whose value is greater than a corresponding threshold value, with a predetermined conversion rate.
Dependencies are inferred from the claim text.