Abstract: There is provided an apparatus and a method of evaluating an effect of chroma downsampling in a compression process of an input image. According to examples of the presently disclosed subject matter the method can include: computing an error for a target chroma downsampling (“CDS”) block based on characteristics of DCT coefficients in the U and/or V planes of a respective CDS candidates group in the input image, and further based on a diversity of the DCT coefficients in the U and/or V planes of the respective CDS candidates group in the input image; and computing an estimated perceptual effect of CDS over the input image based on a plurality of target CDS blocks error values.

Abstract: A method of controlling a compression of an image according to a degree of photo-realism in the image, comprising computing a value indicating a degree of photo-realism for an input image based on a distribution of pixel luminance values within the image, calculating a configuration parameter based on the photo-realism value for the image, and configuring an encoder to compress the image according to the configuration parameter.

Abstract: A system and method for generating a second reduced size digital image from a first digital image, the method including iteratively compressing the first digital image to an extent determined by a quality measure comprising at least a blockiness measure quantifying added artifactual edges along coding block boundaries of the second image and/or use of a quantization matrix generated by computing a weighted average of the quantization matrix of the first digital image and a scaled second quantization matrix.

Abstract: A computerized method for independent disjoint block-level recompression of a first image generated by independent coding of disjoint blocks in a precursor image, the first image having at least one first quantization matrix associated therewith, the method comprising performing at least one independent disjoint block-level compression operation, using a processor on the first image, thereby to generate a re-compressed second image including generating a new quantization matrix and using the new quantization matrix for the independent disjoint block-level compression, including computing a rounding error created by the quantization process utilizing the new quantization matrix and, if needed, adjusting at least one value of the new quantization matrix to reduce a rounding error created by the quantization process utilizing the new quantization matrix.

Abstract: According to examples of the presently disclosed subject matter, a method of controlling a video content system can include: obtaining a current input frame and a preceding input frame from an input video sequence and obtaining a current degraded frame and a preceding degraded frame from a degraded video sequence corresponding to the input video sequence; computing a first differences value from the current input and the preceding input frames and a second differences value from the current degraded frame and the preceding degraded frame, comparing the first and second differences values, giving rise to an inter-frame quality score; computing an intra-frame quality score using an intra-frame quality measure that is applied in the pixel-domain of the current degraded frame and the current input frame and providing a configuration instruction to the video content system based on a quality criterion related to the inter-frame and the intra-frame quality scores.

Abstract: According to examples of the presently disclosed subject matter, a method of controlling a video content system can include: obtaining a current input frame and a preceding input frame from an input video sequence and obtaining a current degraded frame and a preceding degraded frame from a degraded video sequence corresponding to the input video sequence; computing a first differences value from the current input and the preceding input frames and a second differences value from the current degraded frame and the preceding degraded frame, comparing the first and second differences values, giving rise to an inter-frame quality score; computing an intra-frame quality score using an intra-frame quality measure that is applied in the pixel-domain of the current degraded frame and the current input frame and providing a configuration instruction to the video content system based on a quality criterion related to the inter-frame and the intra-frame quality scores.

Abstract: There is provided an apparatus and a method of evaluating an effect of chroma downsampling in a compression process of an input image. According to examples of the presently disclosed subject matter the method can include: computing an error for a target chroma downsampling (“CDS”) block based on characteristics of DCT coefficients in the U and/or V planes of a respective CDS candidates group in the input image, and further based on a diversity of the DCT coefficients in the U and/or V planes of the respective CDS candidates group in the input image; and computing an estimated perceptual effect of CDS over the input image based on a plurality of target CDS blocks error values.

Abstract: There is provided a system, a computer program product, program storage device readable by machine, and a method of downsizing an input disjoint block level encoded image. According to examples of the presently disclosed subject matter, the method can include calculating a DCT downsize ratio for downsizing the input image in a DCT domain according to a target downsize ratio and according to a size of a DCT transform length associated with the input image; adapting an I-DCT according to the DCT domain downsize ratios; performing the adapted I-DCT; providing an intermediate image as output of a DCT domain process; and applying a pixel domain interpolation to the intermediate image according to dimensions of the intermediate image and according to dimensions of the target image.

Abstract: A method of classifying a compressed input image's compression level, comprising applying inverse quantization to DCT coefficients extracted from the compressed input image, giving rise to dequantized DCT coefficients, applying a threshold to the dequantized DCT coefficients, and determining a compression level classification for the compressed input image according to a relation among the threshold and at least one of the dequantized DCT coefficients.

Abstract: A computerized method for independent disjoint block-level recompression of a first image generated by independent coding of disjoint blocks in a precursor image, the first image having at least one first quantization matrix associated there-with, the method comprising performing at least one independent disjoint block-level compression operation, using a processor on the first image, thereby to generate a re-compressed second image including generating a new quantization matrix and using the new quantization matrix for the independent disjoint block-level compression, including computing a rounding error created by the quantization process utilizing the new quantization matrix and, if needed, adjusting at least one value of the new quantization matrix to reduce a rounding error created by the quantization process utilizing the new quantization matrix.

Abstract: There is provided according to an aspect the present invention a method and a system for processing a discrete input image to a reduced-size discrete output image. According to some embodiments, the system may include an interface, a quality parameter controller and an intra-prediction encoder. The quality controller is adapted to provide an encoding-quality parameter enabling a substantial size reduction of the discrete output image, wherein the parameter is related to a target quantitative-similarity measure between the output image and the input image. The intra-prediction encoder is adapted to re-encode the input image, wherein re-encoding includes intra-image prediction, and wherein the encoder is configured in accordance with the encoding-quality parameter.

Abstract: A system and method for generating a second reduced size digital image from a first digital image, the method including iteratively compressing the first digital image to an extent determined by a quality measure comprising at least a blockiness measure quantifying added artifactual edges along coding block boundaries of the second image and/or use of a quantization matrix generated by computing a weighted average of the quantization matrix of the first digital image and a scaled second quantization matrix.

Abstract: A method of classifying a compressed input image's compression level, comprising applying inverse quantization to DCT coefficients extracted from the compressed input image, giving rise to dequantized DCT coefficients, applying a threshold to the dequantized DCT coefficients, and determining a compression level classification for the compressed input image according to a relation among the threshold and at least one of the dequantized DCT coefficients.