Abstract: The present invention is a method and apparatus for converting the resolution of bitmap images, and more specifically, to the use of a template matching process to alter the resolution of digital images for printing or similar methods of rendition. The present invention uses statistically generated templates, implemented using look-up tables, to improve document appearance upon output by converting from an original or input spatial resolution to an output spatial resolution that is device dependent, and where there is a non-integer relationship between the input and output resolutions. The resulting image signals may then be utilized to control a scanning beam where the beam varies in intensity and duration according to the pulses used to control it.

Abstract: High addressability image signals, each representing a pixel in an image, where the signal has one of a relatively large number of signal levels, are directed through an error diffusion quantization process, for the conversion of the signal to one of a relatively small number of levels. Each signal is modified by a correspondingly weighted error correction term signal or signals from previously processed image signals, thereby generating a modified image signal. This modified image signal is compared to a threshold to derive a preliminary output signal having a smaller number of levels. The preliminary output signal is directed to an output if it has the same level as the previous output signal. If the preliminary output signal does not have the same level as the previous output signal, the preliminary output signal is directed to the output only if the previous output signal was one of a contiguous group of a preselected number of like level signals.

Abstract: A bandpass enhancement filter has a pass-band that tracks changes in spatial frequency due to the use of a zooming process upon a digital image signal. The primary pass-band of the enhancement filter is derived from a combination of a plurality of secondary bandpass filter sections, each having a different frequency response and each responsive to a gain adjustment. A control signal reflecting a particular zoom ratio is used in the adjustment of the gain applied to the filter sections, thereby proportioning the output of each filter section so that the combined output tracks the zooming process.

Abstract: A technique for calibrating a cathode ray tube multiformat camera and a video monitor. A video image is corrected on a pixel-by-pixel basis and a gray scale is produced on a photosensitive medium, such as film, and on a monitor with uniform quantization in perceived lightness (i.e., perceived lightness or gray shade varies linearly with digital image code value). Consequently, there is no loss of small-signal and strong-signal structures (detail), and all the image information is recorded on film and clearly displayed on the monitor.

Abstract: A method and apparatus for reducing the distortion of image signals captured by an asynchronous scanning system during a transient period caused by temporarily disabling the scanning operation. Where in during normal operation, the asynchronous scanning system drives a document to be scanned relative to a scanning array which produces image signals representative of the document. Subsequently, the signals are transmitted to a host through an interface at a rate which may exceed the reception rate of the host, the asynchronous operation of the scanning system being regulated by start and stop signals which, respectively, enable and disable the scanning operation.

Abstract: A method of altering the sharpness in the reproduction of an electronically encoded natural scene image, including process steps of: a) converting the signals to a luminance-chrominance signal format, wherein at least one signal represents overall image intensity; b) determining the maximum local contrast within the image; c) determining a filter function applicable to the image which increases maximum local contrast to a predetermined target value, and all other contrast to an amount proportional thereto; and d) applying the determined filter function to the image to increase sharpness thereof.

Abstract: An electronic library which comprises a user interface such as a computer screen, a speaker, a mouse and/or a keyboard; a processor for handling communication with the user and for responding to user requests; and a data store. The data store maintains scanned segments of video data, audio data, or both, and translated replicas of the scanned segments. Searching for specific data is performed by perusing through the translated replicas, but the information that is provided to the user is primarily the scanned segments themselves. The translated versions contain the immediately translatable version of the displayable information and processed information that forms various aggregations of the displayable information. This processing imposes a syntactically logical structure on the displayable information.

Abstract: An image processing system is provided to convert halftone images to continuous tone images. It employs an adaptive filter which processes successive pixels in an input halftone image. The adaptive filter employs a filter that is selected under feedback control from a plurality of filter sets each having a plurality of filters. The halftone image is also low-pass filtered to generate a first approximation image (FAI). A spatial gradient value is computed for each pixel in the FAI. A control operates the adaptive filter to apply one of the predetermined filters to the current pixel as a function of the associated pixel spatial gradient. An output image from the adaptive filter in a first iteration of the filtering procedure can then be applied to the input of the adaptive filter for a second adaptive filtering iteration. Pixel gradients for the second iteration are computed from the image output from the first iteration.

Abstract: An image processing system converts screen structured halftone images to continuous tone images. Value data is sequentially generated for successive pixels of a halftone image. An averaging filter is provided for sequentially filtering each pixel in the halftone image in the horizontal image direction in accordance with a first predetermined filter to generate an intermediately filtered image. A pattern matching filter then sequentially filters each pixel in the intermediately filtered image in the vertical direction to generate a hybrid filtered image. The hybrid filter arrangement is then iteratively operated for three additional sets of orthogonal directions, i.e. the vertical and horizontal directions, a first diagonal direction and a second diagonal direction, and the second and first diagonal directions. The best hybrid image is generated as an output continuous tone image for storage and/or processing to a halftone copy or print.

Abstract: An image data smoothing method smooths image data representing a picture transmitted by a facsimile transmitter and received by a facsimile receiver in the normal mode in printing out the image data so that curves and oblique lines of the picture are reproduced satisfactorily.

Abstract: A data processing system converts a raster image of grey scale value pixels into an image of binary value pixels and diffuses pixel value errors that result from the conversion. The data processing system initially converts a grey scale value pixel to a binary value pixel, determines an error value for the pixel by finding a difference between the pixel's binary value and its previous grey scale value; derives error diffusion values attributable to immediately adjacent pixels in a next line of the raster image and stores those attributable error diffusion values. Upon reaching one of the immediately adjacent grey scale value pixels in the next line, and during a conversion of that pixel from its grey scale value to a binary value, the attributable stored error diffusion values are accessed and combined with the adjacent pixel's grey scale value.

Abstract: A target region and a pin hole size are specified in a block copy image, which is divided into plural separate regions. The size of each separate region in the target region is calculated and compared with the pin hole size. The separate region smaller than the pin hole size is extracted as a possible pin hole area and filled with the color of its surrounding area, thereby the pin holes are eliminated.

Abstract: The contour fidelity of reproduction of images is enhanced by matching groups of pixels with templates based on a hierarchical set of patterns. This is accomplished by isolating a symmetrical window of pixels in the image including a central pixel and matching the groups of pixels in the window with hierarchical templates. Enhancement values for the central pixel are provided based on the results of the comparison. Windows are formed so that each pixel in the image is a central pixel for at least one window. The hierarchial set of patterns is developed so that each pattern in the hierarchy is a combination of an extension pattern and the pattern immediately below it in the hierarchy. This significantly reduces the hardware requirements for implementation of the technique. Templates are developed by creating horizontal, vertical, reversed and inverted permutations of each pattern in the set.

Abstract: A document image scanner that converts scanned images for output as bilevel images is provided with a bilevel image filter. The bilevel image filter counts the number of continuous pattern elements in each direction, vertical, horizontal and diagonal, from a specific point and compares the results with a predetermined reference. Patterns falling below the reference value are regarded as resulting from background noise and are erased.

Abstract: An automatic engraving system scans an image such as a photograph, samples and resizes the image to provide a masterized gray scale data base of the image. The image is then logarithmically corrected and noise is removed from the image using the Outlier noise reduction method. The Outlier noise reduced image is then smoothed and edge detection methods are used to provide an output that represents the initial image filtered smoothed and edge detected. The edge detection image is then converted to a bilevel image using thresholding. The bilevel image is then converted to a vector form and speckle noise removed. The speckle noise removed image is then converted to a vector engraving file which is sent to an engraving machine. The engraving process then can batch create one or more than one image or multiple numbers of a single image. The output can be printed rather than engraved to produce the artistic effect of traditional engraving on paper.

Abstract: An image processing apparatus includes an input unit for inputting multivalue data for each pixel, a resolution conversion unit for generating multivalue data of one pixel corresponding to each block comprising one or a plurality of adjacent pixels of the input multivalue data in order to output multivalue data having a pixel density corresponding to a printing pixel density of a printing unit to the printing unit, and an assigning unit for assigning a magnification ratio of an output image. The resolution conversion unit changes the number of pixels of input image data constituting one block in accordance with the magnification ratio assigned by the assigning unit.

Abstract: Digital image processing apparatus for interpolating a digital input image into an interpolated output image, in one embodiment of the invention, comprises an input buffer (12) for accommodating pixel data of the input image and a coefficient buffer (14) for storing precalculated interpolation weighting coefficients prior to real time image interpolation. The coefficient buffer (14) comprises a first memory segment (22) for containing a set of precalculated sharp interpolating weighting coefficients obtained by using a sharp interpolating algorithm, a second memory segment (24) for containing a set of precalculated soft weighting coefficients obtained by using a soft interpolating algorithm and a third memory segment (26) for containing a set of precalculated weighting coefficients representative of a predetermined characteristic of the input image, such as contrast or density.

Abstract: A resolution conversion method for securing a high quality of pictorial image by converting an pictorial image data of resolution of 200 dpi to an pictorial image data of resolution of 300 dpi so as to print without any deterioration or distortion of the quality of a picture and to prevent for a printer or a displaying device.

Abstract: A method of quantizing pixels in an image formed by a plurality of pixels, each pixel representing an optical density of the image at a location therewith, and having an original optical density value selected from one of a set of `c` original optical density values that has a number of members larger than a desired output set of `d` optical density values, through a process of error diffusion. In this process, `c` and `d` are integer values representing pixel depth. For an input image so comprised, initially, an image signal is initially modified in accordance with previously determined error. Thereafter, during the quantization step of the process, the threshold of an error diffusion process is dynamically adjusted in accordance with the original image to selectively control an amount of edge enhancement introduced into the image.

Abstract: An image processing apparatus performs an edge correction process for image signals of respective pixels sequentially inputted, each image signal having a density level corresponding to a pixel. An edge amount detector of the image processing apparatus calculates a difference between a density level of an image signal of a specified pixel predetermined from among the image signals and a product of a predetermined value and the sum of the density levels of peripheral pixels located at a predetermined distance from the specified pixel, and outputs a detection signal having a level of an edge amount of the calculated difference, and an edge amount convertor converts the edge amount of the detection signal into a converted edge amount in a predetermined manner, and outputs a conversion signal having level of the converted edge amount.

Abstract: An image processing apparatus capable of contracting or enlarging an original image includes a variable scale magnification processing unit for magnifying the original image in accordance with a magnification m, and a digital filter for correcting an image quality. Since weighting matrixes h1-h5 of the digital filter are varied depending on magnification m, a deterioration in image quality can be prevented irrespectively of magnifications.

Abstract: A level of an input luminance signal for a pixel is compared with step values which change stepwise in level in a predetermined range of level, and distribution of the levels of the input luminance signal in the predetermined range of level is represented by a cumulative histogram. Subsequently, a histogram value is derived from the outline of the cumulative histogram, and a compensation value is produced on the basis of the histogram value, and the compensation value is added to the input luminance signal, and hence a compensated luminance signal is output to control the luminance of a video image.

Abstract: A method and apparatus for detection and smoothing of jagged edges in a graphics display is described. The edge detection and smoothing is done using only a pixel-map representation of the pixel colors of the image as input. Edges are detected based upon the color representations of certain groups of pixels. Smoothing of the edges is accomplished by adjusting the color of certain pixels in the region of a detected edge. Edges are detected by successively scanning either sets of two rows or sets of two columns of pixels. Edge detection occurs during the row or column scans by discerning certain sequences of color changes between pairs of adjacent pixels. Color changes are detected only if certain threshold changes in color occur between pairs of adjacent pixels. Unless the threshold color change is exceeded, pixels are considered to be the same color and no edge is detected. Jagged edges are detected and smoothed regardless of the type of color representation used in the pixel-map.

Abstract: An image signal processing apparatus including an image signal output device activated in synchronism with a pixel synchronizing signal for outputting therefrom an image signal which defines, as a variable region, a d.c. level formed between a first d.c. level and a second d.c. level exceeding the first d.c. level, a triangle-shaped wave signal generator activated in synchronism with the pixel synchronizing signal for outputting therefrom a triangle-shaped wave signal which defines, as a variable region, a d.c. level formed between a third d.c. level less than the first d.c. level and the second d.c. level, and a comparator supplied with the image signal and the triangle-shaped wave signal so as to output a pulse-width modulated signal therefrom.

Abstract: An image processing apparatus having: an unit for receiving a digital multi-value pixel data; a D/A converter for converting the inputted multi-value pixel data into an analog signal; a generator for generating an analog pattern signal synchronously with an input of the digital multi-value pixel data; a sample/hold circuit for sampling and holding the analog signal converted by the D/A converter, synchronously with an input of the digital multi-value pixel data; and a binarizing circuit for generating a binarized pulse signal having a width corresponding to the value of the digital multi-value pixel data by comparing the analog signal held the said sample/hold circuit with the pattern signal generated by the pattern signal generator.

Abstract: A bitmap to be prepared for printing by a printing process with a characteristic dilation or erosion artifact, is initially increased in resolution by a selected factor. The bitmapped image is then increased or decreased in size, at the increased resolution, by an amount necessary to compensate for the characteristic erosion or dilation of the printing process. The bitmap is rescanned, or reduced in resolution, to the original resolution of the image. The rescanned image is highly binary in appearance, but will include a number of gray level pixels in areas where it has been increased in size. Prior to printing, the pixel values are subjected to a quantizing process where gray level pixel values are reduced to binary values, preferably through an error diffusion process which operates only on gray pixels. The process of increasing the bitmap resolution may include a step of smoothing halfbitting.

Abstract: A signal processor and method for maximizing the detection range of imaging infrared seekers against ship targets. The invention comprises a bank of two-dimensional spatial filters, having rectangular kernels matched to targets of various aspect ratios and sizes, implemented in a separable form that appears well suited to processing in real-time image data acquired sequentially by column.

Abstract: A high definition image generating system for an image processing apparatus for forming an image by converting multi-level data into dot impact output data of font patterns. The system comprises a block forming circuit for averaging multi-level data by a (2.times.2) block, an edge-direction detecting circuit for detecting an edge direction to output an edge-direction detection signal, an edge detecting circuit for detecting an edge to output an edge detection signal, and a switching circuit for switching a font pattern to be outputted to another pattern according to the edge detection signal and the edge-direction detection signal.

Abstract: A method and an apparatus for processing an image signal generated in an image reading apparatus comprising a light source for illuminating a document, an optical system, and an optical detector for detecting a light which is reflected at a reading point on the document and passes through the optical system and for outputting an image signal corresponding to an amount of light detected thereby are disclosed. A secondary light source effect function which describes a degree that a light reflected at each point other than the reading point on the document affects the image signal corresponding to the reading point is obtained. The image signal output from the optical detector is corrected based on the secondary light source effect function and an image signal corresponding to each point so that a component corresponding to a light which is reflected at each point other than the reading point and affects the image signal corresponding to the reading point is eliminated from the image signal.

Abstract: There is provided an image processing apparatus comprising an image signal generator having a first processing unit for processing the image signal in a first mode and generating a first processed signal, a discriminator for discriminating characteristics of the image signal, the discriminator having a selector for selecting the first processed signal according to a 4 discrimination result; and a pulse width modulated signal generator for processing the first processed signal from the selector by using a pattern signal and for generating a pulse width modulated signal.

Abstract: Briefly, the invention provides a method of enhancing pixel data from a raster image to improve the appearance of the rendered image by modifying morphological artifacts which normally occur in raster image systems. The method commences by applying a window to a portion of the raster pixel data from the raster images to define a block of raster pixel data having a predetermined area. The pattern of the block of raster data within the window is then compared with a plurality of predetermined patterns representing morphological artifacts. A determination is made from the comparison whether a substantial match exists between the block of raster data within the window and one or more of the plurality of predetermined patterns. In the event of a match the block of raster data is modified to provide an enhanced block of raster pixel data free of said morphological artifacts.

Abstract: In a system for reproducing an image pattern data, a decision point designation means exclusively designates a decision point at the corresponding coordinate position in a coordinate region of image pattern reproduction in divisional coordinate regions when a decision point extracted based on a region decision data obtained by region decision means is located in a region of the first kind, exclusively designates a decision point at the scan starting point of a coordinate region of image pattern reproduction when the extracted decision point is located in a region of the second kind, designates no decision point when the extracted decision point is located in a region of the third kind, and, based on the designation by the decision point designation means, a shading of dots of the image is carried out.

Abstract: The invention concerns a method for rendering scene information in images having a large dynamic range, i.e. sunny and shady areas. The method takes particular advantage of image segmentation and computations employed in compression of images for electronic still photography. In distinguishing large areas, the method selectively adjusts the brightness of all portions of the area without necessarily preserving contrast which avoids halo artifacts. Those portions in areas of intermediate size are subjected to a smoothing feature which avoids the production of artifacts in the form of a line at the boundary.

Abstract: There are image processing method and apparatus for use in digital copying apparatuses, facsimile apparatuses, etc. which handle an image signal. This apparatus comprises an edge detector to detect the edge portion of the image signal, a smoothing circuit to smooth the image signal, an edge emphasizer to emphasize the edge of the image signal, and a mixer to mix the output of the smoothing circuit and the output of the edge emphasizer. A mixture ratio of the output of the smoothing circuit and the output of the edge emphasizer is varied in response to the output of the edge detector. The edge detection of the edge detector is performed due to the linear differentiation. With this apparatus, the moire in the case of a mesh original image is removed and the characters and line drawings can be reproduced with a high degree of fidelity.

Abstract: An image reading device makes edge emphasis processing or density conversion processing for an image signal output after reading a film image different according to whether the film image is a negative image or a positive image.

Abstract: A correspondence relation between a structure of a bi-level pattern A and a structure of a bi-level pattern B is statistically learned by use of a learning high-density image. The bi-level pattern A forms a partial region of a low-density character and line image except a screened dot image. The bi-level pattern B forms a corresponding partial region of a desired high-density image. A judgement is made as to whether the low-density image is equal to or different from a screened dot image. Reference pixels are selected from the partial region of the low-density image. The low-density bi-level pattern A is converted into the high-density bi-level pattern B on the basis of a result of the learning by use of the selected reference pixels when the low-density image is different from a screened dot image. A pixel of the low-density image is repeated to convert the low-density image into the high-density image when the low-density image is equal to a screend dot image.

Abstract: In an image processing device for processing image data representing an image, and including an image filtering arrangement, a filter function is applied to the image data that greatly amplifies or enhanced high frequency imge data, including noise inherent in the image. Such noise, which may be the granularity of the image, when enhanced, serves to mask the beating pattern of moire. One function which accomplishes adequate high frequency and noise filtering is a modified Laplacian function with a maximum modulation at a frequency of the noise or granularity of the image. Similarly, the special effect of a random screen image or mezzo tint is obtained when a continuous tone image is processed with the modified Laplacian filtering function, and subsequently thresholded in a thresholding arrangement.

Abstract: A reference original having a reference image is prepared and photoelectrically read with an image reader. The image thus obtained includes a true image and a false image which is called as a ghost or a flare. The relationship between the true image and the false image is detected. Then, an objective image to be reproduced is photoelectrically read with the image reader. The image thus obtained has a true image and a false image of an objective. The false image is eliminated using the relationship detected for the reference original.

Abstract: The present invention relates to a method for enhancing the outline of shapes that occur in an original image which has been obtained by the use of an electro-optical scanner or similar device for the purposes of preparation for printing. The apparatus for reading images comprises the RAM 12 where plural sets of data having the relationships between the difference signal S-U and the enhancement signal K.multidot.(S-U) are stored. By selecting a proper set, the outline enhancement or graininess sublimation threshold setting can be set according color values and other photo aspects of the original, or according to the design of the original image and it's intended use.

Abstract: A colored photographic original is scanned at a multiplicity of points in each of the primary colors red, green and blue to generate a set of image signals for each primary color. The average luminance of the original in each primary color is calculated from the radiation used for scanning and respective first correction signals for scattered light arising during scanning are produced from the average luminances. The correction signal for each primary color is subtracted from each image signal of the corresponding set. The corrected image signals are processed to enhance the image carried by the signals. The processed signals are sent to a printer. Furthermore, the processed signals of each set are averaged and the resulting averages used to produce respective second correction signals for scattered light arising during printing. The second correction signal for each primary color is subtracted from each processed signal of the corresponding set.

Abstract: A system and method for improving the quality of the output of a full-color image on a reproduction device, such as a display on a monitor or printout from a printer, that only consists of a small number of colors in comparison to the number of colors represented by the input signals. The disclosure involves specifying a new quantization method for multi-color images, rendered with orthogonal or separable color image palettes, that takes advantage of the calculations done by error diffusion. Accordingly, the image input signals are processed using the quantization error generated by one color component of a given pixel to influence the quantization of subsequent color components of the same pixel, and in such a way that the color image, so rendered, appears less grainy.

Abstract: The method and apparatus of the present invention performs the quantization, sampling, and final digital image signal reconstruction in a way that reduces quantization artifacts such as contouring while retaining desired spatial (temporal) frequency response and resolution. The technique of the present invention features a spatially varying quantization step, a low pass filtering step, a second spatially varying quantization step, and a comparison step to determine the reconstructed signal.

Abstract: A method for correcting image information deteriorated by flare generated in an image reading unit having a light source for irradiating a document, a scanning system optically scanning the document irradiated by the light source and outputting the image information, and a reference image having a predetermined density distribution is provided. The method includes the following steps of: optically scanning the reference image irradiated by the light source, the scanning system outputting reference image information corresponding to the reference image; generating a function denoting a response with respect to the deterioration of the image information caused by the flare based on the reference image information obtained by the scanning system; optically scanning the document irradiated by the light source by the scanning system; and performing a deconvolution operation in which the image information obtained by the scanning system and the above function are used.

Abstract: Detail enhancement is performed through effectively intensifying an image signal component having a predetermined spatial frequency. Based on the size of an image to be reproduced, a standard observation distance between the image and an observer is computed. A spatial frequency to be intensified is found so that it corresponds to about 12 cpd at the standard observation distance. The size of a pixel area suitable in producing an unsharp signal (U) is set to be inversely proportional to the spatial frequency. Signals (U13-U15) for various pixel areas are prepared, and one of these signals which is obtained for the suitable pixel area is selected to be the unsharp signal (U). An enhanced image signal (S+k(S-U)) is produced on the basis of the unsharp signal and a sharp signal (S).

Abstract: An image processing apparatus includes a control part for allowing real-time operations of a scanning unit and a recording unit, a binarizing part for generating signals indicative of binary data from input data, a preset data generating part for generating either a preset thinning width or a preset thickening width, a thinning circuit for carrying out a choking process in which the binary data is moved either in a main scanning direction or in a sub scanning direction and a portion of an original image is removed so as to obtain a choked image, a thickening circuit for carrying out a spreading process in which the binary data is moved either in the main scanning direction or in the sub scanning direction and an additional image portion is added to the original image so as to obtain a spread image, and an image composition part for generating a composite image of the choked image and the spread image so that a shadow is added to the original image.

Abstract: An image restoration apparatus comprises an image display device for displaying an image estimated as a nondegraded original image, a lens system for focusing the estimated image displayed on the image display device, an image input means for photographing an image focused by the lens system and for receiving the photographed image as image information, a comparing means for comparing the input image information received by the image input means with degraded image information prepared beforehand to obtain a difference therebetween, and a restoring means for performing restoration of an original image by changing the estimated image by using a random number on the basis of the difference calculated by the comparing means.

Abstract: A method of reproducing gray levels on a device capable of displaying a limited number of gray levels. A system is disclosed for partitioning an image composed of pixels into halftone cells, each having multiple pixels. Each input pixel value within a halftone cell is translated into an output pixel value in accordance with a set of threshold arrays.

Abstract: There is provided an improved image reader. In the image reader, light from an object is converted into an analog signal by a photoelectric converter. The signal is quantized by an A/D converter on the basis of top and bottom reference voltages to produce a digital picture signal. A digital picture signal corresponding to a dark current flowing to the photoelectric converter is stored in a memory as a dark current data. Also a digital picture signal corresponding to the optical strength of predetermined level is stored in another memory as a white level data. Then, the top and bottom reference voltages are produced which correspond to the top and bottom quantization-threshold values on the basis of the dark current and white level data, respectively. The top and bottom reference voltages are then respectively applied to the A/D converter to produce the digital picture signal without signal distortion.

Abstract: An image scanning reading system incorporates an image signal processing device for processing an image signal produced by a reading optical system. The image signal processing device includes an unsharp signal generator for averaging image signals S produced when image information on an original is scanned by the reading optical system, thereby to produce an unsharp signal U. The image signal processing device also includes an image signal generator for generating an image signal S' from the image signals S and the unsharp signal U according to the equation:S'=S+K(x).multidot.(S-U)where K(x) is a corrective coefficient selected to compensate for variations of MTF characteristics of the image signals, which variations are caused with respect to scanned positions x on the original by the reading optical system.

Abstract: An image forming apparatus such as a digital color copy machine is disclosed. The image forming apparatus provides an image reader, an amplifier for amplifying image signals read by the image reader, a laser driver for driving a laser diode to form an image on a recording medium and a switching circuit for switching the amplification gain according to the kind of image to be formed.