Abstract:
A digital photography apparatus, particularly a digital still camera, includes circuit portions for acquiring a digital image, and for obtaining a compressed image. The apparatus also includes a memory for storing the compressed image. A processor is provided for obtaining a processed image and corresponding processing parameters from the image acquired. The processor supplies as an output, in a first operative condition, the processed image to be compressed by the compression circuit portion. In a second operative condition, the processor supplies as an output the image acquired to be compressed by the compression portion and the processing parameters to be stored in the memory.

Description:
FIELD OF THE INVENTION 
     The present invention relates to digital photography and, more particularly, to a digital photography apparatus for acquiring a digital image representative of an actual scene. 
     BACKGROUND OF THE INVENTION 
     In a typical digital photography apparatus, and particularly in a digital still camera (or DSC), an image of an actual scene is represented by a matrix of digital values (a digital image). The digital image can be transferred to a computer, sent to a network, or displayed on a television screen, without the need for photographic printing on a physical media and subsequent digitization. Digital images transferred to the computer can be processed with the use of suitable programs and printed directly by a user. This eliminates the cost of films and developing, thereby reducing the time required to produce the photographs. 
     Digital images are typically subjected to a compression process to increase the number of images which can be stored simultaneously in an internal memory of the camera. In cameras which use a proprietary compression algorithm such as, for example, that developed by Kodak, the digital images which typically are acquired partially by a light sensor, are compressed immediately and then saved in the internal memory so as to optimize the compression process. A disadvantage of this approach is that it always requires a computer to decompress and possibly process the digital images and to exchange the digital images with users using other devices. 
     In a different known structure which uses a standard compression algorithm, such as the JPEG algorithm, the partial data acquired by the light sensor are interpolated to produce an actual digital image. The digital images are then compressed and saved in the internal memory. The compressed images can be sent directly to other users or transferred to a computer to be decompressed and displayed by most available image-processing devices. However, this approach also requires a computer to be able to decompress and process the digital images and to be able to send them to other devices. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing background, it is therefore an object of the present invention to avoid the aforesaid drawbacks, such as requiring a separate external computer. This and other objects, features and advantages in accordance with the present invention are provided by a digital photography apparatus comprising: means for acquiring a digital image representative of an actual scene; compression means for forming a compressed digital image; and a memory for storing the compressed digital image. Moreover, the apparatus also preferable includes processing means for obtaining a processed digital image and corresponding processing parameters from the acquired digital image and for supplying as an output, in a first operative condition, the processed digital image to be compressed by the compression means and, in a second operative condition, the acquired digital image to be compressed by the compression means and the processing parameters to be stored in the memory. 
     The apparatus of the present invention processes the digital images directly internally and does not therefore require an external computer. This apparatus has an architecture which is not dependent on the technique used for compressing the digital images and is suitable for the use of any proprietary or standard algorithm. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages of the digital photography apparatus according to the present invention will become clearer from the following description of preferred embodiments thereof, given by way of non-limiting example, with reference to the appended drawings, in which: 
     FIG. 1 is a basic block diagram of digital photography apparatus according to the present invention, and 
     FIG. 2 shows the structure of the image-processing unit of FIG. 1, in detail. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference, in particular, to FIG. 1, there is shown a digital photography apparatus  100  provided, in particular, by a digital still camera. However, the present invention is also suitable for use in different applications such as, for example, in a digital video camera, a portable scanner, and the like. 
     The digital camera  100  includes a digital-image acquisition unit comprising a set of lenses  110  and a diaphragm  115  for supplying an image of an actual scene to a light sensor  120 . When a photograph is taken, the diaphragm  115  is opened and the light corresponding to the image to be acquired is focused by the lenses  110  onto the light sensor  120  for a certain period of time. The light sensor  120  typically includes a charge-coupled device (or CCD). A CCD is an integrated circuit which contains a matrix of light-sensitive cells each of which generates an electrical signal (for example, a voltage) the intensity of which is proportional to the exposure of the light-sensitive cell. The electrical signal generated by each light-sensitive cell is transformed, by means of a suitable analog/digital converter (A/D), into a digital value representative of an elemental area of the image (a pixel). 
     To have a color image, the light is broken down into various components typically corresponding to the colors red, blue and green (or RGB). Corresponding to each elemental area of the image there are three cells which are sensitive, respectively, to the wavelengths of red, blue and green light so as to obtain values indicative of the relative RGB components for each pixel. Generally, to reduce the number of light-sensitive cells, the light sensor  120  does not detect all of the RGB components in each pixel. For example, in half of the pixels only the G components are detected and in the other half, only the R and B components are detected. The digital image thus acquired has blurring which is eliminated (as described below) by interpolation of the partial data detected by the light sensor  120 , A unit  125  controls the digital image acquisition process, sending suitable control signals to the lenses  110 , to the diaphragm  115 , and to the light sensor  120 . 
     The camera  100  includes a compression/decompression unit  130  which can produce a compressed digital image (for example, by reducing the quantity of associated data by a factor of several tens) and can subsequently decompress the compressed image. In the camera  100  according to the present invention, the compression/decompression unit  130  may use either a proprietary compression algorithm such as that developed by Kodak, or a standard compression algorithm such as the JPEG algorithm. The compression/decompression unit  130  is connected to a memory  135  to store the digital images in compressed form. Typically, the memory  135  is provided by a dynamic memory which has a capacity of a few Mbytes and can store several tens of compressed digital images. alternatively, the memory is a flash EPROM which also stores the data in the absence of a supply, and additional external memory cards with capacities of a few tens of Mbytes may also be used. 
     An image-processing unit, (or IPU)  140  is provided in the camera  100  according to the present invention and has a first input (IN 1 ) and a second input (IN 2 ) connected, respectively, to the compression/ decompression unit  130  and to the light sensor  120 . A first output (OUT 1 ) and a second output (OUT 2 ) are connected, respectively, to the compression/decompression unit  130  and to the acquisition-control unit  125 . The light sensor  120  is also connected directly to the compression/decompression unit  130  so that the IPU  140  can be excluded (by-passed). The IPU  140  preferably has a third output (OUT 3 ) connected to an interface unit  145  for connection to external devices such as, for example, a personal computer (PC)  150 , a television set  155 , or a modulator-demodulator (MODEM)  160  for connection to a network, such as the INTERNET. 
     The interface  145  is also connected to a finder  165  preferably formed by a liquid crystal device (or LCD). The finder  165  acts as a view-finder when photographs are being taken, to reproduce the image which is being acquired The finder  165  preferably also enables the photographs to be previewed. In this case, a user can select the best images, immediately canceling those not required. It should be noted that, in a preferred embodiment of the present invention, the compression/decompression unit  130  and the IPU  140  (and possibly also the interface  145 ) are produced in integrated form on a single chip of semiconductor material. 
     A central processing unit (or CPU)  170  controls the different operations of the various components of the digital camera  100  by means of suitable pulses. The CPU  170  is connected to an input device  175  provided, for example, by a set of push-buttons, to enable the user to select the various functions of the digital camera  100 . 
     With reference now to FIG. 2, (the elements already shown in FIG. 1 are identified by the same reference numerals or symbols), the input IN 2  is connected to a unit  205  for enhancing the output of the light sensor  120 . The unit  205  typically modifies, by means of an interpolation process, the digital image acquired, to thereby deduce the missing RGB components to eliminate blurring. The number of pixels is also increased to thereby improve resolution as will be readily appreciated by those skilled in the art. 
     An output TEMP 1  of the interpolation unit  205  is connected to a first input of a multiplexer circuit  210 , the second input of which is connected directly to the input IN 1  of the IPU  140 . The multiplexer  210  transfers one of the two inputs to an output of the multiplexer  210 , in accordance with an appropriate control signal CO-DECOD applied to a selection input of the multiplexer. The output of the multiplexer  210  is connected to a segmentation unit  220  which divides the digital image into several regions. For each region, the segmentation unit  220  deduces various parameters such as high-frequency content, average luminosity, and the like. A unit  225  for automatically determining focus (autofocus) and exposure (autoexposure) is connected to the output of the multiplexer  210  and to an output of the segmentation unit  220 . 
     The values determined by the segmentation unit  220  are weighted appropriately on the basis of the characteristics of the image so as to determine the optimal focus and exposure parameters. “Fuzzy” logic techniques as described, for example, in Shimizu et al., “A New Algorithm for Exposure Control Based on Fuzzy Logic for Video Camera”, IEEE Transactions on Consumer Electronics, Vol. 38, No. 3, p. 617-623, August 1992 and in Haruki et al., “Video Camera System Using Fuzzy Logic”, IEEE Transactions on Consumer Electronics, Vol. 38, No. 3, p. 624-634, August 1992 are preferably used for this purpose. An output of the autofocus and autoexposure unit  225  is connected to the output OUT 2  of the IPU  140  so as to supply these parameters to the acquisition-control unit  125 . 
     A signal output by the multiplexer  210  is also applied to a calculation unit  230  which produces a histogram of the frequency distribution of the image. An automatic exposure-correction unit  235  is connected to the output of the multiplexer  210  and to an output of the calculating unit  230 . The digital image is modified on the basis of the data of the histogram produced by the calculation unit  230  so as to correct exposure problems such as, for example, back-lighting or excessive front lighting. 
     A white-balancing unit  240  is connected to an output of the exposure-correction unit  235  and to the output of the calculation unit  230 . The digital image is further modified so as to correct the color shift of the light towards red (reddish) or towards blue (bluish), dependent on the color temperature of the light source. As in the case described above, “fuzzy” logic techniques are also preferably used in these units. It should be noted, however, that the present invention can also be implemented with different or further units for controlling the digital-image acquisition process. 
     The IPU  140  also contains a noise-level estimation unit  245  connected to the output of the exposure-correction unit  235  and to an output of the white-balancing unit  240 . The unit  245  produces an estimate of the noise dependent on the luminosity of the digital image. A noise-reduction unit  250  is connected to the output of the white-balancing unit  240  and to an output of the estimation unit  245 . The digital image is modified on the basis of the estimation performed by the unit  245  so as to reduce dynamically the effects of the noise introduced by the light sensor, dependent on the noise level and on the spatial characteristics of the image. This is described, for example, in Nakajima et al., “A new Noise Reduction System for Video Camera”, IEEE Transactions on Consumer Electronics, Vol. 37, No. 3, p. 213-219, August 1991 and in G. De Haan et al., “Memory Integrated Noise Reduction IC for Television”, IEEE Transactions on Consumer Electronics, Vol. 42, No. 2, p. 175-181, May 1996. It should be noted that, in this case, the correction carried out will be dependent on the magnitude of the exposure correction effected by the unit  235  since the noise introduced by the light sensor depends on the luminosity of the image. 
     The unit  250  is connected in cascade with a color-tone correction unit  255 . The unit  255  corrects alterations (dependent on the type of illumination) of one or more color categories without altering the other colors of the image. In particular, this improves the quality of representation of the skin color tone in a portrait, or of the sky and of the grass in a landscape as described, for example, in E. J. Lee et al., “Color Enhancement of TV Picture Using RGB Sensor”, IEEE Transactions on Consumer Electronics, Vol. 42, No. 2, p. 182-191, May 1996. Various special effects such as, for example, a mist effect, a “fume” effect and the like are applied to the digital image by a unit  260  connected to an output of the color-tone correction unit  255 . It should be noted, however, that the present invention can also be implemented with different or further units for improving the quality of the digital image. 
     The digital image thus processed by the units  230 - 260  is supplied at an output TEMP 2  of the special effects unit  260 . The output TEMP 2  of the unit  260  and the output TEMP 1  of the interpolation unit  205  are connected, respectively, to a first and a second input of a multiplexer circuit  265  which transfers one of the two inputs to an output of the multiplexer circuit  265 , which is connected to the output OUT 1  of the IPU  140 . This is done in accordance with the control signal CO-DECOD applied to a selection input of the multiplexer. 
     The signal at the input IN 1  of the IPU  140  and the control signal CO-DECOD are also applied to an AND logic unit  270 . An output of the AND logic unit  270  is connected to a unit  275  for correcting alterations (such as a mosaic effect) introduced by the discrete cosine transform (or DCT) encoding method used in the JPEG compression algorithm. It should be noted that the AND unit  270  is advantageously used to prevent any malfunctioning of the unit  275  due to a non-coherent input signal. An example of the construction of the unit  275  is described in T.Jarske et al., “Post-Filtering Methods for Reducing Blocking Effects from Coded Images”, IEEE Transactions on Consumer Electronics, Vol. 40, No. 3, p. 521-526, August 1994. 
     The IPU  140  includes a further multiplexer circuit  280  having a first and a second input connected, respectively, to the output TEMP 2  of the special effects unit  260  and to an output of the unit  275 . The multiplexer  280  also has a selection input to which the control signal CO-DECOD is applied. An output of the multiplexer  280  is connected to a filtering unit  285 , the output of which is connected directly to the output OUT 3  of the IPU  140 . The unit  285  filters the processed digital image according to the external device selected. For example, if the external device is a PC which, typically, is connected to a printer for reproducing the photographs, the filtering unit  285  increases the resolution of the digital image by means of an interpolation process. 
     This process is advantageously also used to apply further processing to the digital image such as, for example, a digital zoom, a change in the ratio of its dimensions (for example, from 4:3 to 16:9) and the like. Alternatively, if the external device is the television set, the digital image is filtered to compensate for the loss of sharpness in the images with highly saturated colors due to a y-correction function which is typically applied to the digital image. The unit  285  is also used for filtering the digital image to be sent to the finder ( 165  in FIG.  1 ), for example, by the application of a control of the dynamic range of the image. A control unit (not shown in the drawing) controls the various functions of the IPU  140  and communication with the CPU ( 170  in FIG.  1 ). 
     To describe the operation of the camera, it is assumed that a photograph is being taken. If the compression/decompression unit  130  uses a standard algorithm (JPEG), the control signal CO-DECOD adopts a first value (for example, 00). In this situation, the multiplexer  210  transmits as an output the signal which is applied to the output TEMP 1  and which is provided by the digital image acquired by the light sensor  120  and suitably interpolated by the unit  205 . This digital image is processed by the units  225 - 260  according to the functions selected by the user by means of the input unit ( 175  in FIG.  1 ). The digital image thus processed is supplied to the output TEMP 2  and is transferred to the output OUT 1  by the multiplexer  265 . The processed digital image is then compressed by the unit  130  and stored in the memory ( 135  in FIG. 1) of the camera. 
     If the compression/decompression unit  130  uses a proprietary algorithm (KODAK), the control signal CO-DECOD adopts a second value (for example, 01). In this situation, the signal applied to the output TEMP 1  is processed in the same manner as in the previous case. The multiplexer  265  transfers to the output OUT 1  the signal at the output TEMP 1 , provided by the digital image acquired by the light sensor  120  and interpolated by the unit  205 . This image is compressed and stored. Processing parameters calculated by the IPU  140  during the previous processing stage are also supplied to the compression/decompression unit  130  and are stored in a suitable structure associated with the compressed digital image. In particular, these parameters are stored in a separate file or in an initial portion of a file containing the compressed digital image, as provided for, for example, in the “FlashPix” format. 
     In both of the above-described operative conditions of the IPU  140 , the processed digital image applied to the output TEMP 2  is advantageously transferred by the multiplexer  280  (by means of the unit  285 ) to the output OUT 3  and then by the interface unit  145  to the finder ( 165  in FIG.  1 ). It should be noted that if a proprietary algorithm is used, the architecture of the present invention allows the processed digital image corresponding to the final product to be supplied to the user also in this situation. 
     In a preferred embodiment of the present invention, the IPU  140  can adopt two further operative conditions to transfer the decompressed digital images to an external device. If a standard compression algorithm is used, the control signal CO-DECOD adopts a third value (for example, 10). In this situation, the signal which is applied to the input IN 1  and which is provided by the processed digital image read from the memory ( 135  in FIG. 1) and decompressed by the unit  130 ), is transferred to the correction unit  275  by the AND unit  270 . The processed digital image is manipulated by the unit  275  and is applied to an input of the multiplexer  280  which transfers it to its output and then to the output OUT 3  of the IPU  140  by means of the filtering unit  285 . Finally, the signal at the output OUT 3  is transferred to the interface unit  145  to reach the external device selected. 
     If a proprietary compression algorithm is used, the control signal CO-DECOD adopts a fourth value (for example, 11). In this situation, the multiplexer  210  transmits as an output the signal which is applied to the input IN 1  and which is constituted by the digital image acquired (read from the memory ( 135  in FIG. 1) and decompressed by the unit  130 ), together with the corresponding processing parameters previously stored. The digital image is processed by the units  230 - 260  in accordance with these parameters. The digital image thus processed is supplied to the output TEMP 2 . The multiplexer  280  transfers this signal to its output and then, as in the previous case, to the external device selected. It should be noted that, in this embodiment of the present invention, the camera can be connected directly to any device such as, for example, a printer, without the need for an external computer. 
     Naturally, to satisfy contingent and specific requirements, one of skill in the art may apply to the above-described digital photography apparatus many modifications and variations, all of which, however, are included within the scope of protection of the invention as defined by the following claims.