QMap - Feature color correction
Feature color correction is mainly designed for the attitude of the aircraft in remote sensing and the color changes brought by the shooting. For example, in high-altitude photography, due to the large distance between the center and the boundary, the center of the image is bright and the periphery is dark; coupled with the influence of the incident angle of the sun, the image has a similar spherical or ellipsoidal projection effect. In addition, according to the characteristics of the scanned image, it conforms to the law of cylindrical projection. Therefore, this software provides a solution with originality to solve the problem of uneven color of the image. Through the combined application of various algorithms in this model, coupled with the unique multi-region restriction of this software, the purpose of color balance transition in multi-image stitching can be achieved.
Now according to the software function interface, the introduction is as follows:
1. Select image and center point
Right-click on the image to select the image. Also, right-click anywhere in the image to select the center point for color correction. The determination of the center point varies according to the color deviation of the image.
2. Red, green and blue channel selection
Supports red, green and blue channels for characteristic color correction independently or in combination. The default is combination.
3. Concave selection
The phenomenon of brightening the center and darkening away from the center is defined as concave. The purpose to deal with is that the color brightness compensation increases as the distance from the center increases. On the contrary, it is outburst. The default selection is Concave.
4. Maximum compensation limit
When compensating the color brightness of each pixel on the image, the compensation value given by the algorithm may be large, which will exceed the color display range. Therefore, it is necessary to make a limit, and the limit is in the range of 0 to 200. When there is no limit, it will be automatically set to 0 or 255 after the color display range is exceeded. 20 is selected by default.
5. Color correction factor
This is a fine-tuning parameter in the range of 0.01 to 1, equivalent to one percent to one hundred percent. It means that the calculated compensation value is multiplied by the correction coefficient as the real compensation value, which plays the role of precise adjustment. The default value is 1.
6. Center brightness compensation
At the selected center of the image, since other surrounding images have a certain deviation at the same point, the center brightness compensation method can be used, and a simple adjustment can quickly achieve the effect of color balance. Design compensation range -80 to 80, the default value is 0.
7. Angle of rotation
Since the characteristic color correction algorithm is directional, it can correct any color deviation in cooperation with the change of the center point position. The angle varies from -90 degrees to 90 degrees, and the default value is 0.
8. Corrected models
a) Spherical type: For vertical orthographic photography, the center is bright and the periphery is darkened. The adjustable parameter X is relative to the plane radius of the sphere. The larger the value, the slower the color compensation change rate from the center to the periphery. Conversely, as the rate of change increases, the color compensation value increases rapidly.
b) Ellipse Paraboloid: For high-altitude photography, the attitude of the aircraft is not level, or the color deviation caused by the incident angle of the sun. Adjustable parameters X and Y, relative to the plane projection of the ellipse paraboloid on the X and Y axes. As the values of X and Y increase, the color compensation value gradually increases.
c) Ellipsoidal surface type: Suitable for color correction in most situations. Adjustable parameters X and Y, relative to the projection of the ellipsoid plane on the X and Y axes. The adjustable parameter Z, relative to the height value on the upper Z axis of the ellipsoid, is proportional to the height value of the aircraft. The larger the value, the slower the rate of change of color deviation compensation.
d) Cylinder type: For the characteristics of the scanned image, the color deviation is related to the distance perpendicular to the flight direction. The adjustable parameter X is relative to the vertical distance of the flight direction, and the adjustable parameter Z is relative to the flying height.
According to the specific situation, the combination of the above models, combined with regional division and image cropping, can solve the problem of color jumping deviation caused by multi-image stitching.
9. Test and Process
Click the "Test" button to quickly test various parameters, check the effect, and deal with it once if you are satisfied.
10. Save and Load Plans
After continuous testing, a set of parameters to solve the problem is obtained. Click the "Save plan" button to save the parameters to a file for repetition and inspection. Click the "Load plan" button to restore the test parameters.
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