JP3456169B2 - Digital camera - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital camera for converting light from an object to be photographed into digital data and recording the same, and more particularly to a digital camera capable of being directly connected to an external printing device for printing. .

[0002]

2. Description of the Related Art In recent years, digital cameras have become widespread in which light is converted into an electric signal by an optical sensor such as a CCD and the electric signal is converted into digital data and recorded in a recording medium such as a flash memory. In a digital camera, image data can be stored and various processing can be easily performed by an individual by using a personal computer or the like, and a photograph can be printed without developing a film by outputting the image data to a printer. Further, due to the improvement in printing quality of printers, it has become possible to print high-quality photographs that are almost indistinguishable from conventional silver halide photographs.

Some digital cameras as described above are directly connected to a printer and execute a print program stored in the digital camera to print an image without using another processing device such as a personal computer. Do,
Some of them can perform so-called direct printing.

[0004]

However, ink jet type printers generally use C (cyan) and M.
Since an image is printed by combining the presence or absence of (magenta), Y (yellow), and K (black) dots, the image data including multi-tone data is converted to binarized data and then sent to the printer. There is a need to. In order to print an image with gradation such as a color image neatly, in order to express one pixel of the original data with a plurality of dots, after converting the image data to data with a high resolution and a larger number of pixels, It was necessary to binarize. Handling of image data having a large number of pixels requires a large amount of memory capacity and processing time.

Particularly in a digital camera, since it is important to reduce the size of the main body in terms of portability, the processing speed of the control device and the available memory capacity may be inferior to those of a personal computer. In many cases, therefore, it takes a long time to print an image directly from a digital camera.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a digital camera capable of speeding up the printing of images during direct printing.

[0007]

[Means for Solving the Problems] Claim 1 or 2 of the present invention
According to the digital camera described above, since the data for a plurality of pixels of the image data including the gradation data indicating a plurality of gradations for each pixel is expanded in the horizontal direction, the gradation data is supplemented.
The pre-recorded number of repetitions without delay.
The image data is added to each pixel of the image data and converted into expanded data including gradation data and the number of repetitions thereof, the expanded data is converted into binarized data, and the binarized data is output to an external printing device. Therefore, the data amount of the enlarged data is reduced, high-speed processing can be performed with a small memory capacity, and the printing speed is improved. In addition, the binarization means
It is input repeatedly because it is binarized while expanding in the direction.
Create binarized data based on 1 line of expanded data
Therefore, even with a small memory capacity, high-speed processing is possible.
Printing speed is improved. By converting the enlarged data from the data of one line of the image data, the data required for printing can be created with a small memory capacity.

[0008]

According to the digital camera of the third aspect of the present invention, the binarizing means binarizes by the error diffusion method. Therefore, multi-tone image data can be binarized so that it looks natural to the naked eye.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a block diagram for explaining the structure of the digital camera 10 of one embodiment of the present invention. The digital camera 10 includes a control unit 11 and a condenser lens 1.
2. CCD (Charge Coupled Devic)
e) 13, A / D converter 14, RAM (Random Access Memory) 15 for temporarily recording image data, memory card 16 for recording compressed image data, and card slot 20 to which the memory card 16 can be attached / detached , A liquid crystal display (LCD) 21 for displaying an image, a VRAM 18 in which data for an image to be displayed on the LCD 21 is stored, an interface 19 for outputting the data in the memory card 16 to an external device, and the like. The digital camera 10 according to this embodiment includes a printer 2 as an external printing device.
The so-called direct printing can be performed by connecting to the printer 2 via the interface 19.

The control unit 11 includes a control unit and a data input / output unit, and executes various control programs to control the digital camera 10 in various ways. In this embodiment,
A direct print program is stored in a recording device such as a flash memory built in the digital camera 10, and direct printing can be performed by the control unit 11 executing the direct print program according to a user's instruction.

The condenser lens 12 is provided with a diaphragm 121 for adjusting the amount of light input to the condenser lens 12. As CCD 13, C (Cyan), M (Magenta),
CCD 13 in which a plurality of image pickup devices having Y (Yellow) and G (Green) complementary color filters are arranged in a matrix
By using, a color image can be taken. The complementary color filter may have three colors of C, M and Y.
A CCD having primary color filters of R (Red), G (Green), and B (Blue) may be used. The RAM 15 is an S-DRAM (Synchronous) having a self-refresh function.
ous Dynamic RAM) is used.

The memory card 16 has image data recorded in a flash memory or the like, which is a rewritable storage medium capable of holding recorded contents without being energized, and is detachably mounted in the card slot 20 of the digital camera 10. Has been done. As the memory card 16, for example, PCMCI
By using a memory card conforming to the A standard or a memory card that can be attached to a PCMCIA card adapter, the contents of the memory card 16 can be directly read / written by a personal computer having a PCMCIA card slot.

3 and 4 show the digital camera 1 of this embodiment.
It is a rear view and a top view showing 0. Digital camera 1
For 0, the user determines the shooting range by the LCD 21 or the optical viewfinder as a viewfinder, and presses the shutter button 101 to shoot.
The control unit 11 can distinguish and recognize “half-push” in which the shutter button 101 is pushed halfway in the movable range and “full-push” in which the shutter button 101 is pushed to the limit or near the limit of the movable range. The user uses the mode switching dial 102 for switching the operation mode of the digital camera to “viewfinder mode”, “LCD mode”, “Off”,
One of the six modes of "playback mode", "direct print mode", and "setup mode" is selected.

The "viewfinder mode" is a mode in which photographing is performed using the optical finder in order to save the power consumption of the digital camera 10. The "LCD mode" is a mode in which shooting is mainly performed using the LCD as a finder. The "playback mode" is a mode in which an image based on the image data that has already been captured and recorded in the memory card 16 is displayed. The "direct print mode" is a mode for connecting the digital camera 10 to an external printer via an interface and printing an image. The “setup mode” is a mode for performing various settings such as the shooting conditions of the digital camera 10. When the mode switching dial 102 is set to the “Off” position, the digital camera 10 is powered off.

Around the LCD 21, input keys 103 to 109 are provided as input means. Control unit 11
Executes the control program according to the selected mode. Then, the input of the shutter button 101 or the input keys 103 to 109 by the user is detected, and the corresponding control is performed. An image quality selection button 111, a strobe selection button 112, and a mode selection button 113 are provided on the top of the digital camera 10. When the image quality selection button 111 is pressed, the recording image quality is changed by changing the compression rate or the number of pixels of the image data. When the strobe selection button 112 is pressed, the strobe light emission mode can be selected from automatic light emission, constant light emission, or no light emission at all times. When the mode selection button 113 is pressed, a normal shooting mode, a close-up shooting mode, an enlarged shooting mode, a panoramic shooting mode, etc. can be switched. Each selection button 111, 11
The contents set by 2 and 113 are segment type L
It is displayed on the CD 114.

Next, the operation of the digital camera 10 of this embodiment will be described. The mode switching dial 102 displays "SH
When set to the "1" position, the viewfinder mode is entered. The LCD 21 is not energized, and the LCD 21 is in a non-display state. Normally, the CCD 13 is not energized, and the operation of the CCD 13 starts when the user half-presses the shutter button 101, and the control unit 11 automatically sets the exposure setting, the focus setting, the white balance setting, and the like. Done. The exposure is determined by the shutter speed and aperture. The user is the optical finder 110
Use to determine the shooting range.

When the user half-presses the shutter button 101 of the digital camera 10, appropriate exposure and focus are set for the image recognized by the CCD 13, and the exposure and focus are fixed while the shutter button 101 is half-pressed.

When the user fully presses the shutter button 101, photographing is started and image data is created.
First, all the charges accumulated in the CCD 13 are once discharged, and then the light condensed by the condenser lens 12 is transferred to the CCD.
13 is input. In the CCD 13, the input light is converted into electric charges according to the amount of light. The electric signal output from the CCD 13 is converted into a digital signal by the A / D converter 14. The digital data output from the A / D converter 14 is transferred by directly designating the address of the RAM 15 without going through the control unit 11 by DMA (Direct Memory Access) for speeding up.

Since the data transferred from the CCD 13 has only one color information for one pixel, the RAM 1
By performing color interpolation processing on the data recorded in No. 5 as described below, image data of, for example, 640 × 480 pixels is created.

First, in this embodiment, the image data is JPEG.
Since the image is compressed and recorded in the (Joint Photographic Experts Group) format, the luminance component Y component of the image necessary for generating the JPEG format data is Y = {G + M + Y + C} × 1/4 = 1/4 {2B +
3G + 2R} and the chroma (color difference) component is RY = {(M + Y)-(G + C)} = {2R-G} BY = {(Mg + C)-(G + Y)} = { 2B-G}, and is calculated by using the color information around the pixel of interest. Of the luminance signal Y and the color difference signal UV thus calculated, the luminance component is 640 × 480 pixels,
The color difference component is calculated by calculating pixels in the horizontal direction in units of 2 pixels, and calculating 32
It is calculated as 0 × 480 pixels. This method is a so-called JPEG compression method called 4: 2: 2, in which color component information is partially arithmetically averaged to compress data. Through the above processing, Y data of 640 × 480 pixels and UV data of 320 × 480 pixels are calculated, and Y data
UV format image data is obtained.

Next, in order to increase the number of recordings on the memory card 16, the image data in YUV format is compressed by the lossy compression method based on the JPEG standard to generate compressed data having a small capacity. JPEG is a commonly used compression method for color images, and the storage image quality can be adjusted by changing the compression rate. In JPEG compression, image data is divided into blocks each having 8 × 8 pixels as a unit,
After performing DCT (discrete cosine transform) in block units, quantization is performed by a predetermined quantization table, and further Huffman coding is performed for compression. The JPEG compression can be performed by software by the control unit 11, and a dedicated circuit can be used for speeding up. The JPEG-compressed compressed data is recorded in the memory card 16.

The mode switching dial 102 indicates "SH
When it is set to the position "2", the LCD mode is set, and the shooting target is displayed as a moving image on the LCD 21. When the user fully presses the shutter button 101, image data is created in the same procedure as in the viewfinder mode. The JPEG-compressed compressed data is recorded in the memory card 16. It may take several seconds to ten and several seconds from the start of recording the image data to the memory card 16 to the completion thereof, and during that time, the image based on the image data is continuously displayed on the LCD 21.

The mode switching dial 102 is "DP"
When set to the position, the direct print mode is set. The user can select a photographic image taken by the digital camera 10 by inputting the input key, specify a print size, and print it by the printer 22. The enlargement ratio of the image data is determined according to the number of pixels of the image data, the print resolution and the print size of the printer 22. For example, 7
When printing with a color inkjet printer having a printing resolution of 20 dpi, the resolution (pixel density) of image data is at least 240 d in order to print beautifully.
It is necessary to be pi or more, and it is more preferable that the resolution is close to the resolution of the printer. For example, in order to obtain a resolution of 720 dpi when printing an image of 640 × 480 pixels with a size of 5.6 × 4.2 cm, the image data is enlarged by about 2.5 times to 1600 × 1200. It must be pixel image data.

FIG. 1 is a flow chart showing the procedure of processing performed by the digital camera 10 during direct printing. FIG. 5 shows a direct print program 30 stored in the flash memory or the like of the digital camera 10 for the control unit 11 to execute the direct print.
It is a block diagram which shows the module group which comprises.

In step S101, the image data instructed by the user for printing is expanded by the expansion module 301 from the JPEG format recorded in the memory card 16 to the YUV format. Decompression is performed in JPEG block units, and 8 lines are decompressed in the vertical direction. In step S102, the first correction module 302 performs edge enhancement and color fringing reduction processing on the YUV format image data. In step S103, the rasterizer 303 converts the YUV format image data into three primary colors of R, G, and B, and performs RGB multi-gradation (for example, 256 gradations) bit image data raster-converted for each color. R
It is developed in a predetermined work area of AM15. Step S10
In 4, the second correction module 304 adjusts the contrast and emphasizes the saturation. Through these processes, the image captured by the digital camera 10 is corrected into an image suitable for printing by the printer 30.

In step S105, the color correction module 305 converts a predetermined line in the horizontal direction of image data in RGB format, in the main scanning direction of the printer head in the case of an ink jet printer, into CMYK format, and for each color data. Create data expanded horizontally. The conversion from RGB to CMYK is CMY calculated in advance corresponding to the space with RGB values as the three axes.
This is performed using the conversion table in which the K value is stored.

The horizontal enlargement includes, for example, as shown in FIG. 6, the gradation data in the horizontal direction for a certain color of the image data includes a sequence of "140, 32, 45, 208 ...",
When this is enlarged 2.5 times according to the print size, “2,3,2,3 ...” corresponds to the coordinates of the image data.
The number of repetitions is added to the gradation data of each pixel of the image data according to the coordinates by using the enlargement table in which the number sequence of “140, 2, 32, 3, 45, 2, 208,
3 ... "is created and stored in the RAM 15. The same applies to enlarging to other magnifications. For example, when enlarging to 3.3 times, "3, 3, 4, 3, 3, 4
Using the expansion table "...", "140, 3, 32,
3, 45, 4, 208, 3 ... "is created. Therefore, as shown in the comparative example of FIG. 6, the capacity of the RAM 15 to be used can be reduced rather than increasing the number of gradation data of each pixel of the image data by the enlargement ratio.

In step S106, the halftone module 306 binarizes the image data enlarged using the error diffusion method. For example, when the range of gradation data indicating the brightness is set to 0 to 255 and the threshold value is set to 128, the print color is dark (gradation degree = 255) if the gradation data is larger than the threshold value, and bright (if the gradation data is small). Gradation degree = 0). Here, taking the case where the gradation data of the pixel of interest X1 is 140 as an example, the gradation degree of the print color is 255 from 140> 128, but this causes a large error and is too dark than the actual gradation (error. : 140-255 = -115).

Therefore, in the halftone processing by the error diffusion method, the error (-115) is diffused by shifting the gradation degree of the pixel (9 pixels in the example of FIG. 7) near the target pixel X1 to the brighter one. By repeating such operations, the gradation of the entire vicinity of the pixel of interest X1 is balanced and the gradation of the entire image is pseudo-approximated to the actual gradation.

For this reason, in the halftone processing, the RAM 1
An error buffer for the number of lines defined by the program is secured on the above 5, and the cycle of writing the calculation result for the target pixel and the read for correction calculation is repeated for the number of error buffers to obtain the binarization target data for each color. Repeat for all (pixels). The error buffer requires at least one line, and may secure two lines, three lines, or more. FIG. 7 shows an example in which an error buffer for two lines is secured. In this example, the error buffer is 5 ×
There are two lines.

In the process of inputting the grayscale data for one line to the halftone module 306, the grayscale data obtained by sequentially reading the data stored in the RAM 15 and the number of repetitions are stored in the register of the control unit, and the grayscale data is stored. Each time you input to the halftone module, the number of repetitions is decreased by 1,
When the number of repetitions becomes 0, the next gradation data and the number of repetitions are read from the RAM 15. For example, when the gradation data 32 is repeated three times from the coordinates corresponding to X1 in FIG. 7, the data is stored in the RAM 15 as "32,3", and the binary values for the coordinates corresponding to X2 and X3 are stored. When calculating the encoded data, the value “32” stored in the register of the control unit 11 is used instead of reading the data from the RAM 15. Therefore, the number of accesses to the RAM 15 is reduced and the processing can be performed at a higher speed than in the case where the gradation data of all the pixels of the enlarged image data shown in the comparative example of FIG. 7 is read from the RAM 15.

In step S107, the processing result of the halftone processing for one line is sequentially fetched from the RAM 15 and transmitted to the printer 22 through the interface 19, and the printer 22 prints based on the received data. Processing is performed.

In the process of inputting the gradation data of a plurality of lines to the halftone module 306, the above-mentioned one line worth is calculated according to the value of the enlargement table corresponding to the coordinates of the image data in the vertical direction, that is, the paper feeding direction of the printer. The input to the halftone module 306 is repeated for the data. The enlargement table may be the same as that used for horizontal enlargement. Therefore, the number of lines of the enlarged data to be created is the same as the number of lines of the original image data, and the same effect as that of vertically enlarging the image data can be obtained. Therefore, as shown in the comparative example of FIG. 7, the processing speed can be improved as compared with the case where the image data is enlarged and enlarged data having a large number of lines is created.

In step S108, it is determined whether or not the vertical enlargement processing, that is, the repetition of the data input to the halftone module 306, has been completed by the number of times of the value in the enlargement table.
Returning to 06, halftone processing is performed again, and the processing result of the next line is obtained. If the vertical expansion has been completed, the process proceeds to step S109.

In step S109, it is determined whether or not the CMYK conversion has been completed for the data of one block of eight lines in the vertical direction, and if not completed, the process returns to step S105, and the next line in the block is half-converted. Performs tone processing. If the vertical expansion has been completed,
It proceeds to step S110.

In step S110, it is determined whether or not the processing of all data is completed. If not completed, the process returns to step S101 and the JPEG next 8-line data is expanded to YUV.

In the embodiment of the present invention described above, the expansion table in which the number of repetitions corresponding to the coordinates is stored is used to calculate the number of data repetitions, but the number of repetitions may be calculated. Further, in this embodiment, each of the modules 301 to 306 that performs processing at the time of direct printing is configured by software, but hardware having the same function may be used.

[Brief description of drawings]

FIG. 1 is a flowchart showing a procedure for performing direct printing by a digital camera according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a digital camera according to an exemplary embodiment of the present invention.

FIG. 3 is a plan view showing a digital camera according to an exemplary embodiment of the present invention.

FIG. 4 is a rear view showing a digital camera according to an exemplary embodiment of the present invention.

FIG. 5 is a block diagram showing the structure of a direct print program of a digital camera according to an embodiment of the present invention.

FIG. 6 is a diagram showing a structure of enlarged data generated by a digital camera according to an exemplary embodiment of the present invention.

FIG. 7 is a schematic diagram illustrating an error buffer used in the error diffusion method in the digital camera according to the embodiment of the present invention.

[Explanation of symbols]

10 digital camera 11 Control unit 12 Condensing lens 13 CCD (imaging means) 15 RAM 16 memory card (recording means) 18 VRAM 19 Interface 22 Printer 30 Direct print program 301 Extension module 302 First correction module 303 rasterizer 304 Second correction module 305 color correction module 306 Halftone module

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-51541 (JP, A) JP-A-5-28071 (JP, A) JP-A-11-112932 (JP, A) JP-A-61- 141481 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 5/225-5/247

Claims (3)

(57) [Claims] 1. An image pickup means for converting light from a subject to be imaged into image data, and a recording means for recording the image data,
A digital camera and means for outputting an image based on the image data to an external printing device, the data of a plurality of pixels of the image data including the gradation data indicating a plurality of gradation for each pixel, image Expand horizontally
Therefore, it is recorded in advance without interpolating the gradation data.
Means for adding the number of repetitions to each pixel of the image data to convert it into enlarged data composed of gradation data and the number of repetitions, and for binarizing the image while vertically enlarging it. , Repeated
Binarization data based on the input expanded data of one line
A digital camera, comprising : a binarizing unit that creates a digital image; and a unit that outputs the binarized data to an external printing apparatus. 2. The enlarged data is one of the image data.
The digital camera according to claim 1, wherein the digital camera is converted from line data. 3. The digital camera according to claim 1 , wherein the binarizing means binarizes by an error diffusion method.