JP4378611B2 - A tilt correction method, a tilt correction program, and a photo printing apparatus with a tilt correction function - Google Patents

Description

  The present invention relates to a tilt correction method for correcting a photographed image having tilt distortion, a program for causing a computer to execute such a method, and a photo printing apparatus having such a tilt correction function.

  In photography, especially when shooting a high-rise building from the ground using a wide-angle lens etc. in a landscape photograph, the upper layer will appear smaller due to perspective, resulting in a shot image in which the high-rise building is tilted, or a relatively small subject in product photography However, in order to obtain a bird's-eye view of the product photograph, even if the photograph is taken from above, the portion farther from the camera becomes smaller, so that the photographed image may be trapezoidally distorted more than the visual impression. Such distortion of the captured image is called trapezoidal distortion or tilt distortion. Conventionally, in order to avoid such distortion, it has been necessary to attach a special lens such as a shift lens.

  In recent years, of course, images taken with a digital camera are naturally converted into digital data by photoelectric conversion from a film using a conventional camera using a silver salt film. It has been proposed to correct.

  As one of them, from the original image displayed on the monitor, two inclined straight lines that should be essentially perpendicular to the ground and parallel to each other are specified by specifying two end points, and within the specified straight lines. The coordinates of two corresponding points corresponding to the two end points obtained by projecting the two end points of the inclined straight line on the vertical line passing through the points are obtained for each inclined straight line, and the two end points of the inclined straight line are converted into the corresponding points described above. In some cases, a tilt correction image is generated by obtaining a perspective transformation matrix and performing perspective transformation of the original image based on the perspective transformation matrix (see, for example, Patent Document 1). With such a tilt correction technique, it is easy to generate a tilt correction image automatically if only two inclined straight lines that are essentially perpendicular to the ground and should be parallel to each other are indicated on the monitor. However, it is not so easy to find two inclined straight lines that should be parallel to each other due to tilt distortion in general landscape photographs and product photographs. This is practically impossible especially with landscape photography.

  As another one, a mapping between a first representative point that specifies the shape of the subject and a second representative point that specifies a region of the image of the subject in the image is specified, and tilt distortion is determined according to this mapping. There is a technology to correct this. Specifically, when a subject such as a poster is photographed, the aspect ratio of the poster is input, and then the vertex coordinates of the four corners of the poster in the photographed image are calculated, thereby making the subject in the photographed image a regular shape. Some obtain a mapping function and thereby create a tilt-corrected image (see, for example, Patent Document 2). Even with this technology, the subject is processed as a plane, so it is effective when the subject is a poster, but when the subject is a landscape, it is difficult to find a representative point that identifies the shape of the subject. If this is mistaken, there will be a problem that the tilt correction does not function sufficiently.

JP 2001-84365 A (paragraph number 0014-0037, FIG. 6) JP 2001-177716 A (paragraph number 0027-0052, FIG. 9)

  In view of the above situation, an object of the present invention is to provide a technique capable of quickly obtaining a satisfactory correction image for a photographed image of a landscape or the like by intuitive and simple operation input setting. .

In order to achieve the above object, the tilt correction method for correcting a shot image having a tilt distortion according to the present invention inputs and sets a reference axis for correcting tilt distortion based on the distortion on the shot image displayed on the monitor. And step for inputting and setting an inclination correction intensity for correcting the inclination distortion, and each pixel located on an edge of the photographed image that is orthogonal to the reference axis and has no inclination distortion. As described above, the reference axis is a linear equation with zero inclination, the inclination of the straight line farthest outside from the reference axis is the inclination determined based on the set inclination correction strength, and the further away from the reference axis, Defining a plurality of linear equations having a large inclination, obtaining an inverse transformation of coordinate transformation in which each of the defined linear equations is parallel to the reference axis, Determining the pixel position of the photographed image corresponding to each pixel after only correction using the inverse transform, and calculating the density value of the target pixel of the tilt correction image from the calculated pixel position based on a density interpolation method. It consists of the steps to find.

  In this configuration, first, a reference axis for correcting tilt distortion based on distortion on a captured image displayed on a monitor, that is, a reference axis in which such tilt distortion does not occur or hardly occurs (the image is 90 degrees). Since the vertical line becomes a horizontal line when rotated, the reference axis is set as a horizontal line here. Of course, it is possible to make an input setting with the vertical line as the reference axis. In any case, in this input setting work, a horizontal line passing through this photographing viewpoint can be easily determined by pointing an operation input device such as a pointing device to a photographing viewpoint in which no distortion occurs. The horizontal axis is the reference axis. The inclination distortion based on the tilt distortion increases as it moves away from the reference axis, but the inclination correction strength is input and set from the maximum inclination distortion obtained intuitively. The inclination correction strength is set to be larger as the inclination distortion seems to be large. Based on these input setting information, a plurality of linear equations having a larger inclination as they move away from the reference axis are defined as a linear equation having zero inclination as the reference axis. At this time, the maximum inclination of these linear equations is limited according to the inclination correction strength described above, and the linear equation defined on the outermost side from the reference axis has the maximum inclination. It is defined so that the slope of the linear equation closer to is smaller. That is, the linear equation is defined outside the linear equation with the gradient being zero, which is the reference axis, while increasing the gradient in order. Next, considering coordinate transformation in which a plurality of linear expressions defined in this way are parallel to the reference axis, this coordinate transformation leveles a pixel group extending obliquely defined by each linear expression. This is a coordinate transformation that corrects so-called tilt distortion. As a process for obtaining the actual corrected image, the pixel position of the original image corresponding to the pixel position in the corrected image is calculated as a conventional means for transforming the original image into the corrected image. The inverse transformation of is used. In general, the pixel position of the captured image corresponding to one pixel of the tilt-corrected image obtained in this way is not an integer, that is, a pixel position that is affected by adjacent pixels. The well-known density interpolation method is used to obtain the target pixel density value of the corrected image. As described above, in this method, a tilt-corrected image in which the tilt distortion is corrected according to the set tilt correction strength is created only by setting the reference axis and the tilt correction strength from the captured image. Therefore, even for images such as landscape photography, the tilt distortion can be eliminated by intuitive judgment.

Further, in the above configuration, since a plurality of linear expressions are defined so as to pass through each pixel that is orthogonal to the reference axis in the captured image and that is located on the edge on the side where no tilt distortion occurs, the above-described inverse transform It is possible to directly associate the pixels of the original image with all the pixels constituting the corrected image using . In other words, most but outside of the captured image both sides partitioned by a linear equation and the reference axis is a vertical trapezoidal shape, the side of the shorter from each pixel of the pixel row which forms the longer side of This is because by drawing a straight line on the side, at least one straight line passes through the pixels inside.

  The present invention also covers a program for causing a computer to execute the tilt correction method described above and a medium on which the program is recorded.

In the present invention, a photo printing apparatus with a tilt correction function that employs the above-described tilt correction method is also subject to rights, and the photo printing apparatus with a tilt correction function is distorted on the photographed image displayed on the monitor. A reference axis setting unit that inputs and sets a reference axis for correcting inclination distortion based on the above, an inclination correction intensity setting unit that inputs and sets inclination correction intensity for correcting the inclination distortion , and the reference in the captured image The reference axis is a linear equation with zero inclination passing through each pixel that is orthogonal to the axis and located on the edge where no tilt distortion occurs, and the inclination of the straight line that is farthest outward from the reference axis is set as described above. and the slope is determined based on the inclination correction intensity, and a linear type setting unit that defines a plurality of linear equation with a large slope farther outward from the reference axis, wherein the defined A coordinate conversion setting unit for obtaining a reverse transformation of a coordinate transformation in which a linear expression is parallel to the reference axis, and a pixel for obtaining a pixel position of the photographed image corresponding to each pixel after tilt distortion correction using the inverse transformation A position calculation unit, a tilt correction image generation unit that calculates a density value of a target pixel of the tilt correction image based on a density interpolation method from the determined pixel position, and a photo that outputs a photo print based on the tilt correction image And a print unit. Naturally, this photographic printing apparatus with a tilt correction function can also obtain all the effects of the tilt correction method described above.

Further, in a preferred embodiment of the photo printing apparatus with a tilt correction function, tilt correction images based on a plurality of different tilt correction strengths are displayed in comparison with the monitor. Since the inclination correction intensity set by the user is determined intuitively while viewing the captured image, an optimal tilt correction image is not always obtained with a single input setting. For this reason, it is advantageous if a tilt correction image based on a plurality of different inclination correction intensities is displayed in comparison with the monitor. It is particularly preferable that the tilt correction images based on the intensity before and after the inclination correction intensity that has been set as input are automatically compared and displayed.
Other features and advantages of the present invention will become apparent from the following description of embodiments using the drawings.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an external view showing a photographic printing apparatus with a tilt correction function that employs the tilt correction method according to the present invention. This photographic printing apparatus is a photographic printer that performs exposure processing and development processing on photographic paper P. FIG. An operation station 1A for processing a photographed image taken from an image input medium such as a print station 1B and a developed photographic film 2a or a digital camera memory card 2b to generate and transfer print data used in the print station 1B. It consists of and.

  This photo printing apparatus is also called a digital minilab, and as can be understood from FIG. The back print unit 13 prints print processing information such as color correction information and frame number on the back side of the photographic paper P, and the print exposure unit 14 cuts the print paper P into the size. A photographed image is exposed on the surface of the photographic paper P, and the exposed photographic paper P is sent to a processing tank unit 15 having a plurality of development processing tanks for development processing. After drying, the photographic paper P, that is, the photographic prints P, sent to the sorter 17 from the transverse feed conveyor 16 at the upper part of the apparatus is collected in a plurality of trays of the sorter 17 in a state of being sorted in order units (see FIG. 1). ).

  A photographic paper transport mechanism 18 is laid to transport the photographic paper P at a transport speed in accordance with various processes for the photographic paper P described above. The photographic paper transport mechanism 18 is composed of a plurality of nipping and transporting roller pairs including a chucker type photographic paper transport unit 18a disposed before and after the print exposure unit 14 in the photographic paper transport direction.

  The print exposure unit 14 applies R (red), G (green), and B (blue) to the printing paper P conveyed in the sub-scanning direction based on print data from the operation station 1A along the main scanning direction. A line exposure head for irradiating laser beams of the three primary colors (1) is provided. The processing tank unit 15 includes a color developing tank 15a for storing a color developing processing liquid, a bleach-fixing tank 15b for storing a bleach-fixing processing liquid, and a stabilizing tank 15c for storing a stable processing liquid.

  A film scanner 20 for obtaining photographed image data from photographed image frames of the photographic film 2a is arranged at the upper position of the desk-like console of the operation station 1A, and is used as a photographed image recording medium 2b mounted on a digital camera or the like. A media reader 21 that acquires photographed image data from various semiconductor memories and CD-Rs that are used is incorporated in a general-purpose personal computer that functions as the controller 3 of this photographic printing apparatus. The general-purpose personal computer is also connected with a monitor 23 for displaying various information, and a keyboard 24 and a mouse 25 as operation input devices used as an operation input unit used for various settings and adjustments.

  The controller 3 of this photographic printing apparatus uses a CPU as a core member and constructs a functional unit for performing various operations of the photographic printing apparatus by hardware and / or software, as shown in FIG. As described above, the functional unit particularly related to the present invention includes a data pre-processing unit 31 that takes captured image data read by the scanner 20 and the media reader 21 and performs pre-processing necessary for the next processing, Graphic user interface (hereinafter referred to as GUI) that generates control commands from creation of graphic operation screens including various windows and various operation buttons and user operation input through such graphic operation screens (using a pointing device such as keyboard 24 and mouse 25). GUI section 33 for constructing An image corresponding to the photographed image data transferred from the data preprocessing unit 31 to the memory 30 in order to generate desired print data based on a control command sent from the UI unit 33 or an operation command input directly from the keyboard 24 or the like. A print management unit 32 that performs processing and the like, a pre-judge print operation such as color correction, a simulated image as a print source image and an expected finished print image, and graphic data sent from the GUI unit 33 are displayed on the monitor 23. And a print data generation unit for generating print data suitable for the print exposure unit 14 provided in the print station 1B based on the processed captured image data for which image processing has been completed. 36 and raw shot image data according to customer requirements Or been processed image processing is completed photographed image data and the like formatter 37 that formats the format for writing to CD-R and the like.

  When the photographic image recording medium is the film 2a, the data preprocessing unit 31 sends the scan data for the pre-scan mode and the main scan mode separately to the memory 30, and performs preprocessing for each purpose. When the captured image recording medium is the memory card 2b, when captured image data includes thumbnail image data (low resolution data), the captured image book is used for the purpose of displaying a list on the monitor 23. It is sent to the memory 30 separately from the data (high resolution data), but if thumbnail image data is not included, a reduced image is created from this data and sent to the memory 30 as thumbnail image data.

  As will be described in detail later, the print management unit 32 converts the warp distortion in the shot image displayed on the monitor 23 and the shot image data developed in the memory 30 when the warp distortion occurs. On the other hand, it includes an image processing unit 70 that performs photo retouching processing such as resolution conversion, color correction, enlargement / reduction, image rotation, image synthesis, filtering (such as blurring and sharpness), and trimming.

  As shown in FIG. 4, the tilt correction means 60 designates a specific portion of the photographed image displayed on the monitor 23 with a specific key of the mouse 25 or the keyboard 24, thereby tilting the horizontal line passing through the specific portion based on the tilt distortion. A reference axis setting unit 61 for input setting as a reference axis for correcting distortion, an inclination correction intensity setting unit 62 for inputting and setting an inclination correction intensity for correcting the tilt distortion, and a straight line with zero inclination for the reference axis As a formula, a linear formula setting unit 63 that defines a plurality of linear formulas having larger inclinations as they move away from the reference axis based on the set tilt correction strength, and each of the defined linear formulas is used as the reference axis. A coordinate transformation setting unit 64 for obtaining an inverse transformation of the coordinate transformation which is parallel to the image, and an image for obtaining the pixel position of the photographed image corresponding to each pixel after tilt distortion correction using the inverse transformation. A position computing section 65, and a tilt correction image generation unit 66. based on the density interpolation from the determined pixel position to determine the concentration value of the target pixel of the perspective correction image.

The principle of the tilt correction by the tilt correcting means 60 configured as described above will be described below.
Here, the upper half of the captured image displayed on the monitor 23 has a tilt distortion based on the distortion in the direction extending from the upper right to the lower left of the screen, and the reverse half of the captured image is generated in the lower half of the captured image. It is assumed that a reference axis passing through a so-called shooting viewpoint in which tilting distortion does not occur is set substantially at the center of the screen.

  First, only the procedure for correcting the tilt distortion occurring in the upper half of the photographed image will be described here, but the procedure for correcting the tilt distortion occurring in the upper half of the photographed image is described below. Can be easily applied to the method of correcting the tilt distortion occurring in

In this tilt correction, as shown in FIG. 5, the upper photographed image located above the reference axis E is converted to image data composed of M × (N + 1) pixels and belongs to the rightmost column so as to correspond to the tilt distortion. A straight line L (n) (n is an integer from 0 to N) drawn from each pixel to the left end is defined. At this time, the pixel position in the lower left corner is set as the origin of these linear expressions. The straight line L (N) that is farthest away from the reference axis E has the maximum inclination. This maximum inclination is expressed by the following equation, where the inclination correction intensity set by the inclination correction intensity setting unit 62 is Sx. It is limited by the required reference inclination α.
α = ((N + 1) / M) × Sx
N / M represents the slope of the diagonal line of the upper photographed image, and since the straight line L (n) described above cannot have a slope larger than this slope, the slope correction strength Sx is a decimal number between 1 and 0. . For example, if the inclination correction intensity Sx is 0.5, the reference inclination α is half the inclination of the diagonal line.

The straight line L (n) described above is represented by the following linear equation:
Y = A (n) · X + B (n),
The slope A (n) of each straight line is the outermost straight line L (N), so A (N) is the largest, and the slope A (0) of the straight line L (0) that coincides with the reference axis E 0, and the slope of the straight line between them needs to increase as the straight line moves away from the reference axis E. From these conditions, the slope A (n) of each straight line is defined as follows:
A (n) = (n / N) × α
For example, A (N) is (N / N) × α, equal to α, and A (0) is 0.
As is apparent from FIG. 6, the value of B (n), which is the Y intercept of the straight line L (n), is obtained by the following equation.
B (n) = n−A (n) × M
As a result, all the straight lines L (n) are defined as follows and can be calculated.
Y = A (n) .X + n−A (n) × M
If X is replaced with a discrete variable m that takes an integer from 0 to (M−1),
Y = Γ (m, n) = A (n) · m + n−A (n) × M (1)
Thus, the Y value group can be obtained by a simple loop calculation.

  As can be understood from FIG. 7, in principle, the pixel P group on the straight line L (N) is moved as the pixel Q group of the first row which is the top row, that is, generally a straight line. By moving the pixel P covering L (n) as the pixel Q group in the (N−n + 1) th row, the tilt distortion is eliminated. Such coordinate conversion can be easily performed by coordinate conversion using the straight line L (n) group. However, as a conventional means for transforming the original image into a corrected image, the pixel position of the original image corresponding to the pixel position in the corrected image is calculated. The pixel position of the original image corresponding to each pixel position of the corrected image is found.

FIG. 8 schematically shows a mechanism for finding the pixel position of the original image corresponding to each pixel position of the corrected image based on such inverse transformation.
For example, regarding the pixel position of the original image corresponding to the pixel Q (1,1) located in the leftmost column in the uppermost row of the corrected image, the column position is the same as the pixel Q of the corrected image from the principle of tilt correction. Obviously, the row position is the value of Y (= Γ (0, N)) obtained by substituting m = 0 and n = N into the above-described equation (1). The position of the pixel of the original image corresponding to the pixel Q (4,4) of the corrected image is (4, Γ (3, N-3)).

  In general, since the value of Y is not an integer but has a decimal number, the pixel value (density value) of the obtained pixel P (1, Γ (0, N)) of the original image is good. It is determined using a known density interpolation method, and the pixel value (density value) is assigned to the pixel Q (1,1). As a density interpolation method, a nearest neighbor method, a bilinear method, a bicubic method, and the like are known. However, since a captured image that is a high-resolution image is targeted here, a bilinear method or a bicubic method is preferable. In this way, the density value of each pixel of the corrected image is sequentially obtained from the corresponding pixel position of the original image.

FIG. 9 shows tilt distortion correction when the tilt direction of the tilt distortion is reversed. Here, the pixel position at the right end of the reference axis E is set to the straight line origin, and the straight line L (n) can be expressed by the following expression by obtaining the procedure described above.
Y = A (n) · X + n
If X is replaced with a discrete variable m that takes an integer from 0 to (M−1),
Y = Δ (m, n) = A (n) · m + n (2)
Thus, the Y value group can be obtained by a simple loop calculation similar to the equation (1).

  Next, in this photo printing apparatus, a typical flow when performing tilt correction as necessary while checking the photographed image frames on the monitor screen will be described.

  The scanner 20 or the media reader 21 is used according to the type of the photo recording medium brought by the customer as the print source, and any digitized photographed image data is sent to the memory 30 through the data preprocessing unit 31. .

  When the photographed image data is loaded into the memory 30, each photographed image frame is sequentially displayed in the photographed image display frame 41 of the operation input screen 40 called a pre-judge screen shown in FIG. In FIG. 10, the 6-frame display screen is selected. A color density correction setting area 42 and a print number setting area 43 are arranged below each captured image display frame 41. The color density correction setting area 42 is provided with setting frames of “yellow”, “magenta”, “cyan”, and “density”, and the correction amount “N” represents neutral and means no correction. The print number setting area 43 is provided with a print number input frame, and “pass” means that printing is not performed. A print condition display field 44 is arranged below the pre-judge screen 40. The print channel name applied to the photo print output, the print size included in the print channel, the necessity of index print, The necessity of media output is shown. The print size indicates the size of the finished photo print P. In this embodiment, the print size is determined by the photographic paper width and the feed length. When the tilt correction processing, color density correction setting, and print number setting for each shot image frame are completed on the pre-judge screen 40, the corresponding shot image data is sent to the print data generation unit 36 and converted into print data.

  When special processing such as tilt correction is performed on a specific shot image frame, it is necessary to display the shot image frame on a larger screen. For this reason, when a photographed image to be processed specially is designated on the pre-judge screen 40 by double-clicking the mouse 25 or the like, a one-frame enlarged screen 50 as shown in FIG. 11 is displayed. An enlarged captured image display area 51 is arranged at the center of the one-frame enlarged screen 50, and an image processing setting frame 52 is arranged at the right end.

  When the one-frame enlargement screen 50 is displayed, although not shown here, a message “Please set the reference axis E for correcting the tilt distortion” is displayed, and the enlarged photographed image display area 51 is so-called. A reference axis E, which is a straight line passing through the captured image viewpoint, which is a point where no tilt distortion has occurred, is set by a click-and-drag operation of the mouse 25.

  The image processing setting frame 52 includes a tilt correction strength setting area 53 for setting the tilt correction strength S described above while viewing a value displayed by operating the slide bar using the mouse 25, and a set reference axis E. And the inclination angle display area 54 for displaying the value of the maximum inclination angle which is the inclination of the straight line set on the outermost side calculated based on the inclination correction strength S, and based on the set reference axis E and the inclination correction strength S. A tilt correction determination button 55 and the like for determining to perform tilt correction are arranged.

  When the tilt correction determination button 55 is pressed, the inclination correction strength S for the lower-side captured image of the reference axis E is set next. Since this setting operation is the same as the setting operation of the inclination correction strength S for the captured image above the reference axis E described above, the description thereof is omitted here.

  When the tilt correction strength S for the lower photographed image is also set and the tilt correction determination button 55 is pressed, as shown in FIG. 12, the tilt-corrected photographed image is displayed based on the conditions set on the previous screen. A main image display area 56 to be displayed, a weak correction image display area 57 that displays a corrected captured image that is one level lower than the set inclination correction intensity, and one rank from the set inclination correction intensity. A strong correction image display area 58 for displaying the corrected captured image with the upper inclination correction intensity, a correction image displayed in the main image display area 56, and a determination button 59a used for determining correction, and a tilt correction. A determination screen including a return button 59b for returning to the previous screen again to reset the condition is displayed. With such a configuration, the most satisfactory tilt correction can be performed.

  In the above-described embodiment, the print station 1B exposes a photographed image to the photographic paper P by the print exposure unit 14 having an exposure engine, and performs a plurality of development processes on the photographic paper P after the exposure. Although the silver salt photographic printing method was adopted, of course, the printing station 1B according to the present invention is not limited to such a method. For example, an ink jet that ejects ink onto a film or paper to form an image. Various photographic printing methods such as a printing method and a thermal transfer method using a thermal transfer sheet can be employed.

  The present invention provides an algorithm for correcting a tilted image having a tilt distortion that occurs in photography using digital image processing, and can be applied to all fields related to photographic printing.

External view of photographic printing apparatus employing tilt correction technology according to the present invention Schematic diagram schematically showing the configuration of the print station of the photo printing device Functional block diagram explaining the functional elements built in the controller of the photo printing device Functional block diagram showing the functional configuration of the tilt correction means Explanatory drawing showing the principle of tilt correction and the mathematical formula used Explanatory drawing showing the principle of tilt correction and the mathematical formula used Explanatory drawing showing the principle of tilt correction and the mathematical formula used Explanatory drawing showing the principle of tilt correction and the mathematical formula used Explanatory drawing showing the principle of tilt correction and the mathematical formula used Pre-judge screen Condition setting screen for tilt correction Judgment screen during tilt correction

Explanation of symbols

23: Monitor 25: Mouse (operation input device)
24: Keyboard (operation input device)
60: tilt correction means 61: reference axis setting unit 62: tilt correction intensity setting unit 63: linear equation definition unit 64: coordinate conversion setting unit 65: pixel position calculation unit 66: tilt correction image generation unit 70: image processing unit

Claims (4)

In the tilt correction method for correcting a shot image having tilt distortion,
A step of inputting and setting a reference axis for correcting tilt distortion based on distortion on the captured image displayed on the monitor;
Inputting and setting an inclination correction intensity for correcting the inclination distortion;
In the photographed image, the pixel passes through each pixel that is orthogonal to the reference axis and is located on the edge where no tilt distortion occurs, and the reference axis is a linear expression with zero inclination , and is farthest from the reference axis. a method and inclination, to define a plurality of linear equation with a large slope farther outward from the reference axis is determined based on the slope of the straight line on the set tilt correction intensity,
Obtaining an inverse transformation of coordinate transformation in which each of the defined linear expressions is parallel to the reference axis;
Obtaining the pixel position of the captured image corresponding to each pixel after tilt distortion correction using the inverse transformation;
Obtaining a density value of a target pixel of the tilt correction image based on a density interpolation method from the obtained pixel position;
A tilt correction method comprising: In the tilt correction program that corrects shot images with tilt distortion,
A function of inputting and setting a reference axis for correcting tilt distortion based on distortion on the captured image displayed on the monitor;
A function of inputting and setting an inclination correction intensity for correcting the inclination distortion;
In the photographed image, the pixel passes through each pixel that is orthogonal to the reference axis and is located on the edge where no tilt distortion occurs, and the reference axis is a linear expression with zero inclination , and is farthest from the reference axis. and the inclination is determined based on the slope of the straight line on the set tilt correction intensity, and ability to define multiple linear equation with a large slope farther outward from the reference axis,
A function for obtaining an inverse transformation of coordinate transformation in which each of the defined linear expressions is parallel to the reference axis;
A function for obtaining a pixel position of the captured image corresponding to each pixel after tilt distortion correction using the inverse transformation;
A function for obtaining a density value of a target pixel of the tilt correction image based on a density interpolation method from the obtained pixel position;
A tilt correction method that causes a computer to execute. In a photo printing apparatus with a tilt correction function for correcting a shot image having tilt distortion,
A reference axis setting unit that inputs and sets a reference axis for correcting tilt distortion based on distortion on the captured image displayed on the monitor;
An inclination correction intensity setting unit for inputting and setting an inclination correction intensity for correcting the inclination distortion;
In the photographed image, the pixel passes through each pixel that is orthogonal to the reference axis and is located on the edge where no tilt distortion occurs, and the reference axis is a linear expression with zero inclination , and is farthest from the reference axis. A straight line setting unit that defines a plurality of straight line expressions having a large inclination as the inclination of a straight line is determined based on the set inclination correction strength, and the distance from the reference axis increases.
A coordinate transformation setting unit for obtaining an inverse transformation of coordinate transformation in which each defined linear equation is parallel to the reference axis;
A pixel position calculation unit that obtains a pixel position of the captured image corresponding to each pixel after tilt distortion correction using the inverse transformation;
A tilt correction image generation unit for determining a density value of a target pixel of the tilt correction image based on a density interpolation method from the determined pixel position;
A photo print unit for outputting a photo print based on the tilt correction image;
A photo printing apparatus with a tilt correction function characterized by comprising: 4. The photo printing apparatus with a tilt correction function according to claim 3 , wherein a tilt correction image based on a plurality of different tilt correction strengths is displayed in comparison with the monitor.

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