Detecting a change between images or in a sequence of images
AssigneeFraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V.
InventorsMichael Schoeberl, André Kaup
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Abstract
Detecting a change between images is performed more effectively when a measure of change is used for the detection that depends on a length of the code blocks to which the images are individually entropy-encoded, and which are allocated to different sections of the respective image, since the length of these code blocks is also available without decoding. This uses the fact that the length or amount of data of a code block directly depends, in large parts, on the entropy and hence on the complexity of the allocated image section, and that changes between images are, with high probability, also reflected in a change of complexity.
Claims13
Apparatus for detecting a change between images or in a sequence of images, each individually entropy-encoded to code blocks of variable lengths, which are allocated to different sections of the respective images, wherein the apparatus is implemented to use, for detecting the change, a measure for the change that depends on a length of the code blocks of the images, wherein the images are encoded in a manner divided into sub bands of different transformation stages by means of a wavelet transformation, and the code blocks represent entropy-encoded versions of transformation coefficient blocks of the sub bands, the apparatus comprising:
- an adder configured to—at least for a first and second one of the images, —for image unit regions into which the respective image is divided according to a respective spatial resolution—add the lengths of those code blocks relating to an image section according to the wavelet transformation that overlaps with the respective image unit region, in a manner weighted in dependence on a ratio of the respective image unit region to the respective image section, to acquire, for the image unit regions of the respective image, one added value each as a measure for a local entropy;
- and
- a calculator configured to calculate the measure for the change in dependence on the added values;
- wherein
- at least one of the adder and the calculator is implemented using hardware.
Method for detecting a change between images or in a sequence of images that are each individually entropy-encoded to code blocks of variable lengths, which are allocated to different sections of the respective image, wherein in the method for detecting the change a measure for the change is used that depends on a length of the code blocks of the images,
- wherein the images are encoded in a manner divided into sub bands of different transformation stages by means of a wavelet transformation, and the code blocks represent entropy-encoded versions of transformation coefficient blocks of the sub bands, the method comprising:
- for at least for a first and second one of the images, for image unit regions into which the respective image is divided according to a respective spatial resolution, adding the lengths of those code blocks relating to an image section according to the wavelet transformation that overlaps with the respective image unit region, in a manner weighted in dependence on a ratio of the respective image unit region to the respective image section, to acquire, for the image unit regions of the respective image, one added value each as a measure for a local entropy;
- and
- calculating the measure for the change in dependence on the added values.
A non-transitory computer readable medium including a computer program comprising a program code for performing, when the computer program is executed by a processor, a method for detecting a change between images or in a sequence of images that are each individually entropy-encoded to code blocks of variable lengths, which are allocated to different sections of the respective image, wherein in the method for detecting the change a measure for the change is used that depends on a length of the code blocks of the images,
- wherein the images are encoded in a manner divided into sub bands of different transformation stages by means of a wavelet transformation, and the code blocks represent entropy-encoded versions of transformation coefficient blocks of the sub bands, the method comprising:
- for at least for a first and second one of the images, for image unit regions into which the respective image is divided according to a respective spatial resolution, adding the lengths of those code blocks relating to an image section according to the wavelet transformation that overlaps with the respective image unit region, in a manner weighted in dependence on a ratio of the respective image unit region to the respective image section, to acquire, for the image unit regions of the respective image, one added value each as a measure for a local entropy;
- and
- calculating the measure for the change in dependence on the added values.
Dependencies are inferred from the claim text.