Abstract: An image processing apparatus includes a brightness extracting element for extracting information relating to brightness from color image data; an image attribute judging element for judging a light-color image portion in a color image; and a brightness change section which changes brightness of the light-color image portion. The image attribute judging element includes a separating device for separating foreground data and background data from the color image data; and a comparing section which, when a difference in brightness between the foreground and the background separated by said separating device is smaller than a predetermined value, judges the foreground data as data of a light-color image portion.

Abstract: In an image processor, multi-level image data are divided into blocks, and compressed in the unit of block. The compressed multi-level image data of a block are converted to compressed bi-level image data without expanding the multi-level image data. For example, the compressed multi-level image data on an image of uniform density are converted to compressed bi-level image data expressed with area gradation. In another image processor, the compressed multi-level image data of a block are converted to compressed multi-level image data, without expanding the multi-level image data. For example, the compressed multi-level image data on an image of bi-level image expressed with area gradation are converted to compressed multi-level image data of a half-tone image.

Abstract: An image processing apparatus has a data conversion unit which converts RGB image data of a document to luminance component and chromaticity component, an optimization process unit which converts the distribution state of the luminance component data and chromaticity component data so as to achieve a distribution from a minimum value to a maximum value of the data within a color space, an encoding process unit which encodes data of each pixel as code data obtained by quantization at a gradient level less than the data within a range of gradient distribution based on mean value information, a memory which stores mean value information, gradient range exponent, and code data of each block obtained by the encoding process in the encoding unit, a decoding process unit which decodes code data in block units based on the mean value information and gradient range exponent stored in the memory, and reverse optimization process unit which returns the distribution state of data of the luminance component and chromatict

Abstract: An image forming apparatus automatically identifying top and bottom of document image based on characteristics with regard to shapes or positions of data, etc. recorded on document. Distribution states of pixel cumulative values in main scanning direction and sub scanning direction of image signals provided by scanning the document, are analyzed and top and bottom of the document image is identified from the result of analysis. Further, it is possible to identify the top and bottom of the document image by analyzing the distribution states the pixel cumulative values in the main scanning direction and the sub scanning direction of the image signals and identifying letter series regions and line segment regions displaced therefrom.

Abstract: In data processing wherein image data are processed by dividing them into blocks, a chroma data W is obtained from the color difference data W.sub.R and W.sub.B, and the color difference data W.sub.R and W.sub.B are corrected according to an amplitude of the chroma data W. For example, if the chroma W is smaller than a prescribed threshold value, the color difference data W.sub.R and W.sub.B are set as zero. Then, the so-called block distortion can be prevented. The degree of the correction may depend on the amplitude of the chroma data W. On the other hand, DC coefficients of discrete cosine transform coefficients of adjacent blocks are compared with each other. When the DC coefficients are different from each other, block distortion occurs if they represent a same image. Then, if differences of DC coefficients of discrete cosine transform coefficients of adjacent blocks are small with each other, the DC coefficients are corrected to tend to have similar values.

Abstract: Image data of a pixel matrix are subjected to orthogonal transformation to coefficient data, which are then quantized with a first quantization table for character image and with a second quantization table for half-tone image. Image data are discriminated as character image data or half-tone image data according to the quantization data. The quantization data corresponding to the discrimination are subjected to entropy coding. Image data can be divided into first processing blocks of m*m pixel matrices and second processing blocks of M*M pixel matrices where M>m. A second processing block includes one first processing block and adjacent pixels. Image data in first and second processing blocks are subjected to orthogonal transformation to coefficient data. Coefficient data of the second processing block indicates whether the image is a character image, a dot image, or a half-tone image, permitting selection of an appropriate quantization table.

Abstract: A method and device for processing image data for a document includes the steps of reading RGB image data for the document; dividing the document image data into a plurality of blocks including a prescribed pixel matrix; calculating an average value information and a gradation range index for each of the blocks; converting the data for each pixel of each of the blocks into coded image data based on the average value information and the gradation range index so that the coded image data defines each pixel with fewer gradation levels than the original image data; storing in a memory unit the gradation range index and coded data, which were obtained for each block through the converting step; forming letter distribution histograms for a primary scanning direction and a secondary scanning direction for each block determined to belong to a letter image; identifying a direction in which letters of the document are aligned based on a number of change points in the histogram for the primary scanning direction and a n

Abstract: In an electrophotographic copying machine, image quality is improved by suppressing phenomena such as narrowing and thickening of a linear image or discharge noises in a photograph image due to anomalies on transfer of a toner image. For example, a document type is discriminated and when a transfer brush is used for transfer, transfer current and pretransfer erasing are controlled according to the type of document image. The pretransfer erasing is controlled in various following situations: Bi-level exposure method or multi-level exposure method, edge emphasis, photoelectric efficiency, the surface potential of the photoconductor, and position of a developing device.

Abstract: An image forming apparatus automatically identifying top and bottom of document image based on characteristics with regard to shapes or positions of data, etc. recorded on document. Distribution states of pixel cumulative values in main scanning direction and sub scanning direction of image signals provided by scanning the document, are analyzed and top and bottom of the document image is identified from the result of analysis. Further, it is possible to identify the top and bottom of the document image by analyzing the distribution states the pixel cumulative values in the main scanning direction and the sub scanning direction of the image signals and identifying letter series regions and line segment regions displaced therefrom.

Abstract: In a data processor, in order to perform coding efficiently, image data of a prescribed pixel matrix is subjected to orthogonal transformation to coefficient data. Obtained coefficient data is quantized with a first quantization table for character image, and they are also quantized with a second quantization table for half-tone image. Then, the image data is discriminated to be a character image data or a half-tone image data according to the two quantization data. Then, quantization data in correspondence to the discrimination is subjected to entropy coding. In a different data processor, in order to discriminate a kind of image in a processing block fast and correctly, image data are divided into first processing blocks of m*m pixel matrices and second processing blocks of M*M pixel matrices wherein M>m. For example, m=8 and M=16. A second processing block includes one of first processing blocks and adjacent pixels around it.

Abstract: In a data processor, in order to discriminate the kind of image in a processing block quickly and correctly, image data is divided into first processing blocks of m*m pixel matrices and second processing blocks of M*M pixel matrices wherein M>m. The second processing block includes the data of the first processing block and adjacent pixels around it. Image data in the first and second processing blocks are subjected to orthogonal transform to generate coefficient data. The image type is discriminated as a character image, a dot image or a half-tone image according to the coefficient data of the second processing block and an appropriate quantization table is then selected. Having identified the appropriate quantization table based on analysis of second processing block, image data of the first processing block is quantized according to the thus selected quantization table and quantized data is thereby coded.

Abstract: In reading out an original image divided into a plurality of regions, a scanner reads out image data having each divided region partially repeated for each adjacent divided region. The read out image data of each divided region is stored in a memory in correspondence with the original image and stored in a memory. A controller identifies an overlapping region of the stored image data, and joins each image data according to the identified result to generate an image data corresponding to the original image.

Abstract: In data processing wherein image data are processed by dividing them into blocks, a chroma data W is obtained from the color difference data W.sub.R and W.sub.B, and the color difference data W.sub.R and W.sub.B are corrected according to an amplitude of the chroma data W. For example, if the chroma W is smaller than a prescribed threshold value, the color difference data W.sub.R and W.sub.B are set as zero. Then, the so-called block distortion can be prevented. The degree of the correction may depend on the amplitude of the chroma data W. On the other hand, DC coefficients of discrete cosine transform coefficients of adjacent blocks are compared with each other. When the DC coefficients are different from each other, block distortion occurs if they represent a same image. Then, if differences of DC coefficients of discrete cosine transform coefficients of adjacent blocks are small with each other, the DC coefficients are corrected to tend to have similar values.

Abstract: In data processing wherein image data are processed by dividing them into blocks, a chroma data W is obtained from the color difference data W.sub.R and W.sub.B, and the color difference data W.sub.R and W.sub.B are corrected according to an amplitude of the chroma data W. For example, if the chroma W is smaller than a prescribed threshold value, the color difference data W.sub.R and W.sub.B are set as zero. Then, the so-called block distortion can be prevented. The degree of the correction may depend on the amplitude of the chroma data W. On the other hand, DC coefficients of discrete cosine transform coefficients of adjacent blocks are compared with each other. When the DC coefficients are different from each other, block distortion occurs if they represent a same image. Then, if differences of DC coefficients of discrete cosine transform coefficients of adjacent blocks are small with each other, the DC coefficients are corrected to tend to have similar values.

Abstract: In a data processor, image data of a pixel matrix is subjected to orthogonal transformation to coefficient data, the coefficient data is quantized with a first quantization table for character image and a second quantization table for half-tone image, and the image data is discriminated to be character image data or half-tone image data according to the quantization data. The selected data is then coded. In another processor, image data are divided into first and second processing blocks of m*m and M*M pixel matrices wherein M>m and the second processing block includes one of first processing blocks and adjacent pixels. Image data in a first and second processing block are subjected to orthogonal transformation to coefficient data.