A binary image of an input image is generated, and a character region within the binary image and a region surrounding each character are acquired as character segmentation rectangle information. A thinning process is executed on a region within the binary image which is identified based on the character segmentation rectangle information to acquire a thinned image. An edge detected image of the region identified based on the character segmentation rectangle information is acquired. Whether each character identified based on the character segmentation rectangle information is a character to be separated from a background by the binarization process or not is determined based on a result of a logical AND of the thinned image and the edge detected image.

In one or more embodiments, an image processing apparatus obtains a shade image representing shade components included in a multi-valued image obtained by capturing an image of a document. The shade components depend on an image capture environment. The apparatus binarizes a pixel value of a target pixel in the multi-valued image based on a pixel value of a corresponding pixel in the shade image at coordinates identical to those of the target pixel to generate a pixel value representing white or black. One or more image processing methods and storage mediums are also provided herein.

An example embodiment may involve obtaining an mn pixel cell from an input image. Each of the mn pixels in the mn pixel cell may be associated with at least one color value. An mn attribute cell may be determined, elements of which may be associated in a one-to-one fashion with respective pixels in the mn pixel cell. The mn pixel cell may be compressed in a lossy fashion, and the mn attribute cell may be compressed in a lossless fashion. Compression of the mn pixel cell may be based on at least part of the mn attribute cell. An interleaved representation of the compressed mn pixel cell and the compressed mn attribute cell may be written to an output medium.

An image processing device includes a controller. The controller is configured to perform: acquiring image data having a plurality of objects; calculating an amount of characteristic of each of the objects, the amount of characteristic indicating a degree of change in pixel values; setting a process order based on the amount of the characteristic of each of the objects; setting a target value, the target value being a reference value to reduce a data size of the image data; reducing an object data size of at least one of the plurality of objects based on the process order in such a way that the data size of the image data becomes smaller than or equal to the target value, thereby generating a reduced object; and generating reduced image data having a data size smaller than the data size of the image data by using the reduced object.

There is provided an image processing apparatus. A splitting unit splits an image into a block. A quantization unit performs quantization of the block using a plurality of methods. A calculating unit calculates a distance between the block and a result of the quantization. A selecting unit selects a quantization result of the quantization unit using the distance. An encoding unit performs fixed-length encoding of the quantization result selected by the selecting unit. The quantization unit includes a first quantization unit that preserves texture in the block, and a second quantization unit that represents pixels in the block in a plurality of colors.

An image processing apparatus includes an area extracting unit and a table image detecting unit. The area extracting unit is configured to extract halftone dot areas and character images in an image. The table image detecting unit is configured to detect the extracted halftone dot areas as a table image if (a) the extracted halftone dot areas include no ruled lines, (b) plural halftone dot areas among the extracted halftone dot areas are arrayed in a primary scanning direction and/or a secondary scanning direction, and (c) the arrayed plural halftone dot areas include the character images at at least two positions.

A method for compressing an image, includes: calculating a level of hues of the image over at least all of one layer of the image; depending on the type of hues of the representative layer, classifying the image in one of the following three classes: a first class if the image is of a graphics type; a second class if the image is of a highly contrasted type; a third class if the image is of a low-contrasted type; and, choosing a compression processing type depending on the class of the image: difference processing, if the image is of the first class; frequency processing, if the image is of the third class; and, if the image is of the second class: for lossless or low-loss compression, preferably using difference processing, and, in the other cases preferably using frequency processing.

In low-resolution processing (reduction processing) in which input image data is separated into character print data and image print data to generate print data of lower resolution than that of the input image data, if a plurality of pixels is simply reduction-processed to one pixel, color of a color image surrounding a character may change. In an image processing method, calculation for performing reduction processing so that the plurality of pixels in the input image data corresponds to one pixel in the print data is performed as follows. A ratio of using a pixel value of a character attribute pixel in the calculation is set to 0, or set smaller than a ratio of using a pixel value of an image attribute pixel. As a result, a change in the color of the color image surrounding the character can be prevented.

A color conversion device includes color conversion sections, an obtaining section and a reconversion section. The color conversion sections perform color conversion in parallel to convert colors of pixels contained in image data of a predetermined number of rows. The predetermined number is two or more. For the color conversion, at least one color conversion section uses certain color conversion information, and the other color conversion section uses other color conversion information having an information amount less than that of the certain color conversion information. The obtaining section obtains attribute information indicating an attribute of each of the pixels. When the attribute information is predetermined attribute information, the reconversion section converts a pixel color-converted with the other color conversion information using a pixel color-converted with the certain color conversion information in a predetermined pixel area contained in the image data.

In an image processing apparatus for encoding image data and a method of controlling the same, whether an attribute of each of a plurality of areas in image data corresponds to an edge in an image based on the image data is determined, and one of a plurality of sub-sampling processes is selected according to the determination for each of the plurality of areas. Note that the plurality of sub-sampling processes can sub-sample color difference components of each of the plurality of areas by different processes. By the sub-sampling process selected as that corresponding to each of the plurality of areas, each of the plurality of areas is sub-sampled to encode the image data.