JP2010103934A - Image processing apparatus, digital camera, and image processing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus for obtaining a result equal to conventional contour processing with computational complexity reduced as compared with the prior arts. <P>SOLUTION: When a subject image is imaged by an imaging element 15, an image signal is output to a control circuit 16. The control circuit 16 performs various kinds of image processing on the image signal, and calculation processing of a feature amount is performed on the image signal by a feature amount calculator 16a. Thereafter, an image corrector 16b performs predetermined arithmetic operation on luminance values of pixels on the basis of the features value calculated by the featured value calculator 16a. Predetermined compression processing or the like is performed after the arithmetic operation, thereby creating image data. The created image data are recorded onto a storage medium 22. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for controlling the strength of an image outline.

Image processing capable of blurring or enhancing the outline of an image is known. In performing such processing, for example, an image filter having a size of 3 × 3 or 5 × 5 is generally applied. For example, Patent Document 1 discloses an image filtering method that enhances the contour of an image by scanning the image with an m × n image filter.
Japanese Patent No. 3512581

  For example, when a 5 × 5 image filter is applied, one pixel is processed using 25 pixel values. Therefore, when the target image to be processed is large or when iteratively processing a plurality of images, there is a problem that a huge amount of calculation is required.

  The invention according to claim 1 is an input unit for inputting an image signal, and for each pixel included in the image signal input to the input unit, the luminance value of the target pixel to be processed and the luminance value of adjacent peripheral pixels The feature amount calculating means for calculating the feature amount by converting the difference between the Euclidean distance and the feature value calculated by the feature amount calculating means for the luminance value of each pixel included in the image signal input to the input means An image processing apparatus comprising: an operation unit that performs a predetermined operation based on a quantity.

  According to a fourth aspect of the present invention, there is provided a digital camera comprising the image processing apparatus according to any one of the first to third aspects, wherein a signal obtained from an image sensor is input as the image signal.

  The invention according to claim 7 is an input step of inputting an image signal, and for each pixel included in the image signal input in the input step, a luminance value of a target pixel to be processed and a luminance value of adjacent peripheral pixels A feature amount calculation step of calculating a feature amount by converting the difference between the two into a Euclidean distance, and a feature value calculated by the feature amount calculation step with respect to a luminance value of each pixel included in the image signal input in the input step An image processing program that causes a computer to execute a calculation step of performing a predetermined calculation based on a quantity.

  According to the present invention, a result equivalent to that of the conventional contour processing can be obtained with a smaller calculation amount than the conventional one.

-First embodiment-
FIG. 1 is a block diagram showing a circuit configuration of a digital camera according to this embodiment. The digital camera 1 includes an input device 13, a focus adjustment device 14, an image sensor 15, a control circuit 16, a DRAM 17, a flash memory 18, an LCD drive circuit 19, a liquid crystal monitor 20, and a memory card interface (I / F) 21.

  The imaging element 15 is configured by a CCD or CMOS image sensor including a plurality of photoelectric conversion elements corresponding to pixels. The imaging element 15 captures a subject image formed on the imaging surface and outputs a photoelectric conversion signal (image signal) corresponding to the brightness of the subject image. R (red), G (green), and B (blue) color filters are provided on the imaging surface of the imaging element 15 so as to correspond to the pixel positions, respectively. Since the image pickup device 15 picks up a subject image through the color filter, the image signal output from each image pickup device has RGB color system color information.

  The image signal output from the image sensor 15 is input to the control circuit 16. The control circuit 16 performs various image processing on the image signal to generate image data. Then, the control circuit 16 performs compression processing on the generated image data by a predetermined method such as JPEG, and records it in the storage medium 22 as an image file in a format such as EXIF. The control circuit 16 is composed of, for example, a RISC and controls each circuit shown in FIG.

  The control circuit 16 performs a known focus evaluation value calculation based on a detection signal output from an AF sensor module (not shown), and outputs the calculation result to the focus adjustment device 14. The focus adjustment device 14 moves the photographing lens 10 to a position where the focus evaluation value is maximized based on the calculation result.

  The DRAM 17 is used to temporarily store data during or after image processing, image compression processing, and display image data creation processing. The display image data is generated by the control circuit 16 based on the image data generated by the control circuit 16 based on the output from the image sensor 15 or the image data recorded in the storage medium 22. The generated display image data is stored in the DRAM 17 by the control circuit 16. The flash memory 18 is a non-volatile memory in which various processing programs for the operation of the control circuit 16 are recorded, for example.

  The LCD drive circuit 19 drives the liquid crystal monitor 20 based on a command from the control circuit 16, and the liquid crystal monitor 20 displays an image based on display image data stored in the DRAM 17. The liquid crystal monitor 20 displays various setting menu screens of the digital camera. The input device 13 includes various operation buttons such as a release button and a playback button, and outputs an operation signal of each operation button by the user to the control circuit 16.

  The control circuit 16 includes a feature amount calculation unit 16a and an image correction unit 16b. The feature amount calculation unit 16a calculates a feature amount based on the Euclidean distance for all the pixels included in the image signal. The image correction unit 16b performs a predetermined calculation on the luminance value for each pixel based on the feature amount for each pixel calculated by the feature amount calculation unit 16a. The image processing performed on the image signal output from the image sensor 15 executed by the control circuit 16 includes calculation of the feature amount by the feature amount calculation unit 16a and calculation on the luminance value by the image correction unit 16b.

  Next, the feature amount calculated by the feature amount calculation unit 16a will be described. The feature amount calculation unit 16a calculates a feature amount for all the pixels included in the image signal based on the adjacent pixel in the right direction and the adjacent pixel in the downward direction. This feature amount is calculated using a luminance value of the pixel such as an I component in the HSI color space.

  FIG. 2 is a diagram for explaining a feature amount calculation procedure. FIG. 2 shows nine pixels (P11, P21, P31, P12, P22, P32, P13, P23, and P33) that are aligned starting from the upper left of the figure. For example, the pixel P11 is located at the coordinates (1, 1), and the pixel P21 is located at the coordinates (2, 1). In addition, in the quadrangle representing each pixel, a numerical value representing the luminance of the pixel is described. For example, the luminance value of the pixel P11 is 60, and the luminance value of the pixel P21 is 70.

  The feature amount calculation unit 16a calculates the feature amount of all the pixels included in the image signal using the following equation (1).

  Here, C (x, y) represents the feature amount of the pixel at coordinates (x, y), and I (x, y) represents the luminance value of the pixel at coordinates (x, y). The above equation (1) is an equation in which the luminance values of the three pixels are regarded as two points on the plane, and the Euclidean distance between the two points is the feature quantity C (x, y). That is, the Euclidean distance between the point (I (x, y), I (x, y)) and the point (I (x + 1, y), I (x, y + 1)) is the feature quantity C (x, y ).

  From the definition, if the luminance value of an adjacent pixel changes greatly, the feature amount becomes large. On the other hand, when the luminance value of the adjacent pixel changes gently, the feature amount becomes small. For example, consider calculating the feature amount C (1, 1) of the pixel P11 in FIG. At this time, I (1,1) is the luminance value 60 of the pixel P11, I (2,1) is the luminance value 70 of the pixel P21, and I (1,2) is the luminance value 40 of the pixel P12. When these values are applied to the equation (1), the characteristic amount C (1, 1) of the pixel P11 becomes 22. On the other hand, in the case of the pixel P12 in which the difference in luminance value from the surrounding pixels is larger than that of the pixel P11, the feature amount is 50.

  Next, the calculation to the luminance value by the image correction unit 16b will be described. The image correction unit 16b adds or subtracts the feature amount for each pixel calculated as described above by the feature amount calculation unit 16a to the luminance value of each pixel.

  FIG. 3 is a diagram illustrating a first example of the addition / subtraction process to the luminance value performed by the image correction unit 16b. Hereinafter, in order to simplify the description, the pixel group 31 arranged in a line in the horizontal direction as shown in FIG. 3A will be described. The contents described below can be applied to the pixels arranged in the vertical and horizontal directions shown in FIG. 2 in the same manner as in FIG.

  Now, it is assumed that the pixel group 31 arranged in a line in the horizontal direction shown in FIG. 3A has the luminance values shown in the graph in FIG. As shown in FIG. 3B, the luminance values of adjacent pixels change gently. FIG. 3C shows the feature amounts calculated by the feature amount calculation unit 16a for these pixels. As shown in FIG. 3B, in the pixel group 31, the luminance value of the adjacent pixels is gradually changed, so that the feature amount of the pixel shown in FIG. 3C is a small value.

  The image correction unit 16b adds or subtracts the feature amount shown in FIG. 3C with the luminance value shown in FIG. Whether the addition or subtraction is performed is determined by the calculation mode set in the digital camera 1 by the user. FIG. 3D shows a result obtained by subtracting the feature amount shown in FIG. 3C from the luminance value shown in FIG. 3B by the image correction unit 16b. Since the feature amount is a small value, the overall luminance value gradually decreases. Similarly, FIG. 3E shows the result of adding the feature amounts shown in FIG. 3C by the image correction unit. As in the case of subtraction, the overall luminance value gradually increases. As described above, in the pixel group 31 of the first example, since the brightness value of the adjacent pixel does not include a rapid change, the brightness value is not greatly changed.

  FIG. 4 is a diagram illustrating a second example of the addition / subtraction process to the luminance value performed by the image correction unit 16b. Similarly to FIG. 3, it is assumed that the pixel group 41 shown in FIG. 4A has the luminance value shown in FIG. In the pixel group 41, there is a portion where the luminance value greatly changes in adjacent pixels as compared to the pixel group 31 in FIG. Therefore, a large value can be confirmed in the feature amount of the pixel group 41 shown in FIG.

  FIG. 4D shows the result of subtracting the feature amount shown in FIG. 4C from the luminance value shown in FIG. 4B, and FIG. 4E shows the result of addition. In FIG. 4D, it can be seen that in a group of pixels having relatively large luminance values, the luminance values of the pixels located before and after the group are greatly reduced. That is, the luminance value subtraction processing by the image correction unit 16b has an effect of reducing the light amount with respect to the contour of the image. As a result, the contour of the image is enhanced.

  On the other hand, in the feature value addition result shown in FIG. 4E, the luminance values of the pixels located before and after the group of pixels having relatively large luminance values are greatly increased. That is, the addition processing to the luminance value by the image correction unit 16b has an effect of increasing the light amount with respect to the contour of the image. As a result, the contour of the image is blurred.

  Next, a specific processing flow from the imaging to the recording of image data including the image processing by the distance calculation unit 16a and the image correction unit 16b described above will be described with reference to the drawings.

  FIG. 5 is a diagram showing a flow of processing from imaging to recording of image data. First, in step S <b> 1, a subject image is picked up by the image pickup device 15, and an image signal is output to the control circuit 16. In step S2, the control circuit 16 performs various image processing on the image signal. In step S3, a feature amount calculation process is performed on the image signal by the feature amount calculation unit 16a. Note that the control circuit 16 may execute the processes of step S2 and step S3 in order or in parallel.

  In step S4, the image correction unit 16b performs an operation on the luminance value of each pixel based on the feature amount calculated in step S3. In step S5, predetermined compression processing or the like is performed, and image data is created. In step S6, the image data created in step S5 is recorded on the storage medium 22.

According to the digital camera according to the first embodiment described above, the following operational effects can be obtained.
(1) The image correction unit 16b adds and subtracts the feature amount based on the Euclidean distance, which the feature amount calculation unit 16a calculates using the luminance values of the adjacent pixels in the right direction and the downward direction, to the luminance value. Thereby, the sharpness of the outline of an image can be weakened or strengthened.
(2) The feature amount calculation unit 16a calculates a feature amount of one pixel based on two pixels, a pixel adjacent in the right direction and a pixel adjacent in the downward direction. Thereby, the feature amount corresponding to each pixel can be calculated with a small amount of calculation.
-Second embodiment-
In the first embodiment described above, the image processing by the feature amount calculation unit 16a and the image correction unit 16b is performed when image data is recorded on a storage medium. The digital camera according to the second embodiment performs similar image processing when displaying an image on a liquid crystal monitor.

  Hereinafter, an operation when the live view function is enabled in the digital camera of the present embodiment will be described. When the live view function is enabled, the control circuit inputs an image signal from the image sensor 30 times per second. The image signal at this time does not include the pixel values of all the pixels included in the image sensor, but some pixels are thinned out in accordance with the resolution of the liquid crystal monitor.

  The control circuit executes correction processing on the image signal by the feature amount calculation unit and the image correction unit, as in the first embodiment. Thereby, display image data in which the contour is emphasized is obtained. Then, the display image data is displayed on the liquid crystal monitor by the control circuit.

  Furthermore, the digital camera according to the present embodiment multiplies the feature amount by a predetermined coefficient when adding and subtracting the feature amount to the luminance value. This coefficient may be arbitrarily set by the user, or may be automatically set according to the intensity of ambient light measured by the digital camera. When the coefficient is larger than 1, the influence of the feature amount on the luminance value is increased. Conversely, when the coefficient is smaller than 1, the influence of the feature amount on the luminance value is reduced.

According to the digital camera according to the second embodiment described above, the following functions and effects can be obtained in addition to the functions and effects obtained by the digital camera according to the first embodiment.
(1) The control circuit performs image correction processing on the image signal input from the image sensor, and then displays an image created based on the image signal on the liquid crystal monitor. As a result, an image with an enhanced outline is displayed on the liquid crystal monitor, so that the visibility of the liquid crystal monitor is improved.
(2) The intensity of the correction process applied to the image displayed on the liquid crystal monitor is determined based on ambient light or a user instruction. Thereby, the fall of the visibility of the liquid crystal monitor resulting from the operating environment of a digital camera can be suppressed.

The following modifications are also within the scope of the present invention, and one or a plurality of modifications can be combined with the above-described embodiment.
(1) The calculation by the image correction unit is not limited to addition and subtraction, but may be other calculations. For example, it may be based on an arbitrary function.
(2) A predetermined coefficient may be added to Expression (1) for calculating the feature amount. For example, I (x + 1, y) −I (x, y) may be multiplied by a coefficient larger than 1 so that the difference in luminance value with the right adjacent pixel has a greater influence on the feature amount.
(3) The correction processing by the feature amount calculation unit and the image correction unit may be executed at a time other than when shooting and when the live view function is enabled. For example, the correction process may be executed when an image recorded on the storage medium is displayed, or may be executed when the image recorded on the storage medium is processed and re-recorded. Good.
(4) When calculating the feature amount, a pixel other than the pixel adjacent in the right direction and the pixel adjacent in the downward direction may be referred to. For example, the feature amount may be calculated using pixels adjacent in the left direction and pixels adjacent in the upward direction.
(5) The control circuit of each embodiment described above may be a CPU that executes a predetermined control program stored in the flash memory. In this case, each process executed by the control circuit in each embodiment is realized by the CPU executing a predetermined control program.

  As long as the characteristics of the present invention are not impaired, the present invention is not limited to the above-described embodiments, and other forms conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention. .

It is a block diagram which shows the circuit structure of the digital camera by 1st Embodiment. It is a figure explaining the calculation procedure of a feature-value. It is a figure which shows the 1st example of the addition / subtraction process to the luminance value performed by the image correction part 16b. It is a figure which shows the 2nd example of the addition / subtraction process to the luminance value performed by the image correction part 16b. It is a figure which shows the flow of a process from imaging to recording of image data.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Digital camera 15 Image pick-up element 16 Control circuit 16a Feature-value calculation part 16b Image correction part 22 Storage medium

Claims (7)

An input means for inputting an image signal;
For each pixel included in the image signal input to the input means, a feature amount for calculating a feature amount by converting a difference between a luminance value of a target pixel to be processed and a luminance value of an adjacent peripheral pixel into a Euclidean distance A calculation means;
A calculation unit that performs a predetermined calculation on the luminance value of each pixel included in the image signal input to the input unit based on the feature amount calculated by the feature amount calculation unit;
An image processing apparatus comprising: The image processing apparatus according to claim 1.
The image processing apparatus, wherein the calculation means adds the feature amount to a luminance value of each pixel as the predetermined calculation. The image processing apparatus according to claim 1.
The image processing apparatus, wherein the calculation means subtracts the feature amount from a luminance value of each pixel as the predetermined calculation.   The digital camera provided with the image processing apparatus as described in any one of Claims 1-3 which inputs the signal obtained from the image pick-up element as the said image signal. The digital camera according to claim 4, wherein
A digital camera characterized in that an image signal subjected to a predetermined calculation by the calculation means is stored in a storage medium. The digital camera according to claim 4 or 5,
An image is displayed on the basis of an image signal subjected to a predetermined calculation by the calculation means. An input process for inputting an image signal;
For each pixel included in the image signal input in the input step, a feature amount for calculating a feature amount by converting a difference between a luminance value of a target pixel to be processed and a luminance value of an adjacent peripheral pixel into a Euclidean distance A calculation process;
A calculation step of performing a predetermined calculation based on the feature amount calculated by the feature amount calculation step for the luminance value of each pixel included in the image signal input in the input step;
An image processing program for causing a computer to execute.