JP2624962B2 - Image processing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus that performs color image processing based on input color signals.

2. Description of the Related Art Conventionally, a recording apparatus capable of performing color recording using a plurality of color inks is known. A multi-colored character can be recorded by using a color ribbon even with a print impact printer, but a dot printer such as an impact type or an ink jet type using a plurality of color inks and ink ribbons is required to record a color image. .

An image recorded by such a printer may be an image synthesized by a computer or the like, or an image input from a video camera or the like.

[Problems to be Solved by the Invention] In particular, when an image is input from a video camera or the like, color correction may have to be performed due to a difference between the color temperature setting of the camera and the color temperature setting of the lighting at the time of shooting. . Further, in order to record an image of a desired color tone, color correction may be performed.

However, with conventional printers, color adjustment requires procedures such as adjusting the color density of inks of colors such as cyan, magenta, yellow, and black, and changing the overall gamma. Often it was bothersome and impossible.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image processing apparatus capable of easily performing a correction process desired by a user and improving color reproducibility in an output image.

[Means for Solving the Problems] In order to achieve the above object, according to the present invention, there are provided input means for inputting a digital luminance signal and two digital color signals, which constitute a digital color image signal; Instruction input means for inputting a user's manual instruction regarding the correction level of the two digital color signals; and a shift for each of the two digital color signals using conversion data corresponding to each of the two digital color signals based on the manual instruction. An amount is obtained, and a configuration having a correction unit for performing a correction process on the two digital color signals based on the obtained shift amount is employed.

[Operation] According to the above configuration, the shift amount for each of the two digital color signals is obtained by using the conversion data corresponding to each of the two digital color signals based on the user's manual instruction regarding the correction level of the two digital color signals. Is calculated, and color correction is performed by performing a correction process on the two digital color signals based on the obtained shift amount.

EXAMPLES Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

FIG. 1 is a block diagram of a printer employing the present invention. The apparatus shown in FIG. 1 inputs a video signal of the NTSC system (Japan-US system) and outputs a color image by a subtractive color recording head such as an ink jet system.

In this embodiment, when the timing is specified by a predetermined switch (freeze switch described later) on the switch console, the image at that time is recorded and output as a still image.

The input NTSC signal is decoded by the decoder circuit, and Y (luminance), R
The signal is demodulated into -Y, BY (color difference signal).

As is generally known, Y (luminance signal) represents lightness, and RY and BY (color difference signals) represent saturation.

The Y signal is converted into a digital signal by the A / D converter 2a, and is taken into the image memory 3. On the other hand, the RY and BY color difference signals are A / D-converted by the A / D converter 2b line by line for each scanning line, and are taken into the image memory 3.

When the above-mentioned image is fetched into the memory, the timing is designated by the freeze switch 15a of the switch console, and is started in accordance with the synchronization signal. A synchronization signal control circuit 10 is provided to synchronize the timing of data capture on the video circuit side and the recording side.

Printing of the captured image data is started by turning on the print switch on the switch console. Memory 3
Reading from and output control are controlled by the CPU 14. The control is performed using the ROM 13a and the RAM 13b.

The CPU 14 calls the Y data and the color difference data of the place to be printed from the memory 3. Since the color difference data is line-sequential, it is linearly interpolated between the scanning lines to obtain RY, BY
Data is produced. A method of using the data of one of the upper and lower scanning lines without interpolation (so-called twice output) may be used.

The Y data output from the memory 3 is input to the luminance compression circuit 4 where gradation conversion is performed. This circuit can be realized by a conversion table that receives a highlight point (Hp) and a dark point (Dp) of an image and input Y data and outputs converted data Y ′. Hp and Dp are specified from the switch console 15.

This conversion has the meaning of compressing the dynamic range of the video signal to a reproduction range that can be expressed by ink without changing the saturation.

FIG. 2 shows the conversion characteristic curve in this table. Second
In the figure, a total of 16 conversion characteristic curves are shown, each having four stages of Dp and Hp.

Although Dp and Hp can be input from the switch console, it is also possible to adopt a form in which after inputting the freeze switch 15a, the Y signal memory is scanned to obtain a histogram, Dp and Hp are automatically found and input to this circuit.

Here, the color correction circuit 5 will be described in detail. The color correction circuit 5 has a function of outputting the two color difference signals (RY) 'and (BY)' after inputting and correcting the two color difference signals of RY and BY.

The color conversion circuit 6 converts the two color difference signals into a hue signal (H),
This is a circuit for generating a saturation signal (C). The hue signal (H) and the saturation signal (C) are generated from the color difference signal according to the following equation.

The color conversion circuit 6 can be realized by a table converter that outputs data obtained by the above equation according to the combination of the input color difference signals.

The masking and black generation circuit 7 converts the Y
This is a circuit which receives signals, H and C signals as inputs and converts them into four color density signals of C ", M", Y "and Bk (black) actually used for printing. .

(RY) '= C.cosH (BY)' = C.sinH R '= Y' + (RY) 'G' = Y '-(0.3. (RY)' + 0.11・ (BY) ′) / 0.59 B ′ = Y ′ + (BY) ′ C ′ = − log R ′ M ′ = − log G ′ Y ′ = − log B ′ Bk = Min (C ′, M ', Y') Also, to correct for the asymmetric color component of the ink used A matrix operation as in the above equation is performed.

The masking circuit 7 receives Y ', H, and C as inputs,
It can be realized by a table converter that outputs C ", M", Y ", and Bk. The output signals of C", M ", Y", and Bk are input to the head driver circuit 8, and are output from the D / A converter. Is used to form a driving pulse waveform of the head 9 for recording, and the recording head 9 is driven to perform printing.

The recording head 9 is configured by a color head of an ink jet system or the like that can record four colors of cyan, magenta, yellow, and black.

 Next, the processing of the color correction circuit 5 will be described in detail.

Generally, when the set color temperature does not match the actual color temperature of the subject, a color reproduction error appears as a shift on a chromaticity diagram. This will be described with an actual example. Consider the case where the color temperature of the light source illuminating the subject is 4000 ° K.

If the color temperature set by the camera is 4000 K, it goes without saying that an image with a good color tone can be obtained. However, if the image is taken at a temperature of 3000K on the camera side, the image is corrected excessively, and the image is actually taken as a bluish color.

FIG. 3 is a chromaticity diagram using RY and BY as coordinate axes.

Conversely, when the camera is photographed at a setting of 5000K, the correction is insufficient because the color temperature is higher than the actual one. After all, RY
FIG. 4 shows a chromaticity diagram using XY and BY as coordinate axes.

As can be seen from FIGS. 3 and 4, a color temperature setting error is expressed as a "shift" of color reproduction in a certain direction on the color difference plane. Therefore, it can be seen that the color temperature setting error can be corrected by shifting the color difference signal by the correction amount. In the present embodiment, a case where the above is performed by table conversion will be described.

The table converters constituting the color correction circuit 5 include RY,
The two-color difference signal of BY and I / O from the switch console 15
The correction amount ΔC is input via the port 11 and (R−
Y) ′ and (BY) ′ are output as corrected color difference signals. Here, it is assumed that there are three correction steps in the high color temperature direction and three steps in the low color temperature direction. That is, there are a total of seven levels of ΔC, −3, −2, −1, 0, +1, +2, +3. The method of producing the output signal is as follows.

(R−Y) ′ = R−Y + α · ΔC (B−Y) ′ = R−Y + β · ΔC That is, the two color differences are controlled by one variable ΔC. Here, α and β are arbitrary constants, and may be set so that each step is switched evenly. The number of input bits for two color difference is 8 bits each, 3 bits in 7 steps,
Since 12 bits are required for the address bus, it can be realized with 32KROM.

 Next, the correction input and the movement of the correction will be described.

Color temperature correction switch 15c on switch console 15
Generates a 3-bit digital signal as the correction amount ΔC, and its output is input to the I / O port 11. CPU
14 searches the state of the I / O port 11 for each print of one line, applies the set position data to the color correction circuit 5, and switches the conversion table to perform correction.

According to the above-described configuration, first, a color difference signal is formed, and color correction is performed by shifting the color difference signal based on a desired correction amount. The circuit (or software) for that can be greatly simplified. Therefore, it is possible to realize a color printer that outputs an input image after correcting the color with an inexpensive configuration.

Although an example in which a video signal based on an NTSC signal is recorded and output has been described above, an image signal in another format can be processed by changing the configuration of the decoder.

In the present embodiment, the conversion is performed by table conversion. However, a method of adding or subtracting a correction amount by software may be used.

According to the present invention, the shift of each of the two digital color signals is performed using the conversion data corresponding to each of the two digital color signals based on a user's manual instruction regarding the correction level of the two digital color signals. Since the color correction is performed by calculating the amount and performing the correction process on the two digital color signals based on the obtained shift amount, the correction process desired by the user can be easily performed, and Good color reproducibility, and
Stable correction processing can be realized with a simple circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an image processing unit of a color recording apparatus adopting the present invention, FIG. 2 is a diagram showing a compression characteristic of a color signal, and FIGS. FIG. 9 is an explanatory diagram showing a shift in color data caused by a difference in setting of the color data. DESCRIPTION OF SYMBOLS 1 ... Decoder, 2a, 2b ... A / D converter 3 ... Image memory, 4 ... Luminance compression circuit 5 ... Color correction circuit, 6 ... Color conversion circuit 7 ... Masking and black generation circuit 8 ... ... Head driver, 9 ... Recording head 14 ... CPU

Claims (1)

(57) [Claims] 1. An input means for inputting a digital luminance signal and two digital color signals constituting a digital color image signal, and an instruction input means for inputting a user's manual instruction regarding a correction level of the two digital color signals. And calculating a shift amount for each of the two digital color signals using conversion data corresponding to each of the two digital color signals based on the manual instruction, and based on the obtained shift amounts, the two digital color signals. An image processing apparatus comprising a correction unit that performs a correction process on a signal.