Method and apparatus for image data processing
View Patent ↗An image data processing method and apparatus for performing image correction processes for a restored image data file obtained from a JPEG-compressed image data file which may prevent block distortions and provide a high quality image. A JPEG-compressed data file is read from the storage medium by the reading section, which is restored at the restoring section. The restored data is then split into a low-frequency component and a high-frequency component at the splitting section. The low-frequency component is subjected to the white balance, density, and gradation adjustments at the first image correction processing section and combined with the high-frequency component at the combining section to obtain a combined image data. The combined image data is then subjected to the sharpness adjustment at the sharpness adjusting section, which is outputted from the output section to a printer and reproduced as a printed image.
1. An image data processing method for implementing a gradation adjustment to a restored image data file obtained by restoring a compressed image data file comprising the steps of:
determining whether to perform a gradation hardening operation or a gradation softening operation for said gradation adjustment; and
performing said gradation adjustment; wherein
said gradation hardening operation comprises the steps of splitting said restored image data file into a low-frequency component and a component other than said low-frequency component; performing said gradation hardening operation for said low-frequency component to obtain a gradation-corrected low-frequency component; and combining said gradation-corrected low-frequency component with the component other than said low-frequency component; and
said gradation softening operation comprises the step of performing said gradation softening operation over the entire portion of said restored image data file.
2. An image data processing apparatus for implementing a gradation adjustment to a restored image data file obtained by restoring a compressed image data file comprising:
a gradation adjustment type determining means for determining whether to perform a gradation hardening operation or a gradation softening operation for said gradation adjustment;
a gradation hardening means for performing said gradation hardening operation, comprising a splitting means for splitting said restored image data file into a low-frequency component and a component other than said low-frequency component, a gradation hardening means for performing said gradation hardening operation for said low-frequency component to obtain a gradation-corrected low-frequency component, and a combining means for combining said gradation-corrected low-frequency component with the component other than said low-frequency component; and
a gradation softening means for performing said gradation softening operation over the entire portion of said restored image data file.
3. The method of claim 2 comprising means for restoring a compressed image data file, and wherein the gradation softening means produces a reduced contrast directly to the restored compressed image data without frequency division, and wherein the gradation hardening means increases a contrast in the low frequency component only.
4. The method of claim 3 , wherein determining whether to perform gradation hardening includes a contrast analysis over an entire image and if the contrast analysis exceeds a predetermined threshold, applying the gradation hardening in the low frequency component only.