Image correcting device, method for creating corrected image, correction table creating device, method for creating correction table, program for creating correction table, and program for creating corrected image
View Patent ↗An image correcting device includes an image input section, an image storage section, a correction table storage section, a geometry correcting section for geometrically correcting an input image stored in the image storage section, based on a correction table, and an image output section for output of the input image corrected by the geometry correcting section, wherein the correction table is created by calculating longitudes and latitudes that correspond to respective pixel positions on an output image that becomes the corrected image; calculating corrected latitudes through correction of the latitudes, based on the longitudes and the latitudes; calculating light directions in a subject space, the light directions corresponding to the longitudes and the corrected latitudes; and calculating positions on the input image as resampling positions, the positions corresponding to the respective light directions; and associating the resampling positions with the pixel positions on the output image.
1. An image correcting device for creating a corrected image through geometrical correction of an input image, comprising:
an image input section configured to input the input image;
an image storage section comprising a memory and configured to store the input image;
a geometrical correcting section comprising a circuit and configured to geometrically correct the input image stored in the image storage section by calculating longitudes λ and latitudes Φ that correspond to respective pixel positions on an output image as the corrected image based on cylindrical projection for map projection; by calculating corrected latitudes φ, based on a function f(λ) and the latitudes Φ; by calculating light directions in a subject space, based on the longitudes λ and the corrected latitudes φ; by calculating positions on the input image as resampling positions, based on the light directions; and by associating the resampling positions with the pixel positions on the output image; and
an image output section configured to output the input image corrected by the geometrical correction section, as the corrected image, wherein
the corrected latitudes φ are calculated according to
φ=tan −1 {tan(Φ)· f (λ)}, and wherein
in a region where an absolute value of the longitude λ is larger than or equal to zero and smaller than or equal to π/2, the region being within a domain of the longitudes λ used for correction, the function f(λ) satisfies cos (λ)≦f(λ)≦1.
2. An image correcting device according to claim 1 ,
wherein, the longitudes λ and the latitudes Φ are calculated based on Mercator projection for map projection.
3. An image correcting device according to claim 1 , wherein the function f(λ) satisfies
f (λ)=α+(1−α)cos(λ), 0<α<1.
4. A method for creating a corrected image through geometrical correction of an input image, comprising the steps of:
inputting the input image;
storing the input image;
geometrically correcting the input image stored by the step of storing the input image, by calculating longitudes λ and latitudes Φ that correspond to respective pixel positions on an output image as the corrected image based on cylindrical projection for map projection; calculating corrected latitudes φ, based on a function f(λ) and the latitudes Φ; calculating light directions in a subject space, based on the longitudes λ and the corrected latitudes φ; calculating positions on the input image as resampling positions based on the light directions; and associating the resampling positions with the pixel positions on the output image; and
outputting the input image corrected by the step of geometrically correcting, as the corrected image, wherein
the corrected latitudes φ are calculated according to
φ=tan −1 {tan(Φ)· f (λ)}, and wherein
in a region where an absolute value of the longitude λ is larger than or equal to zero and smaller than or equal to π/2, the region being within a domain of the longitudes λ used for correction, the function f(λ) satisfies cos (λ)≦f(λ)≦1.
5. A non-transitory computer-readable medium, comprising a computer program for creating a corrected image by executing the method according to claim 4 .
6. A method for creating a corrected image according to claim 4 ,
wherein, the longitudes λ, and the latitudes Φare calculated based on Mercator projection for map projection.
7. A method for creating a corrected image according to claim 4 ,
wherein the function f(λ) satisfies
f (λ)=α+(1−α)cos(λ), 0<α<1.