Image Analysis. Preprocessing ROI Image Geometry. Preprocessing. To makes the primary data reduction and analysis task easier.
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ROI Image Geometry
image crop process is the process of selecting a portion of the image, a sub-image, and cutting it away from the rest of the image that\'s how the border was removed in fig3.2.l(b).
Figure 3.2-1 Preprocessing examples. a) an image needing border removal, b) the image after the border is removed, c) an image where only shape information is necessary in order to control a robotic gripper, d) the image after unnecessary information removal which leaves only the object shape
zoom process can be done in numerous ways, a zero- order hold or a first-order hoId.
Figure 3.2-2 Zooming Methods a) Original image. The ape’s face will be zoomed, b) Image enlarged by zero-order hold, notice the blocky effect, c) Image enlarged by first-order hold. Note the smoother effect
Although the implementation of the zero-order hold is straightforward, the first-order hold is more complicated.
Another method that achieve a similar result requires a mathematical process called convolution.
The convolution process requires us to overlay the mask on the image, multiply the coincident values, and sum all the results.
0(0) + 1/2(0) + 0(0) + 1/2(3) + 1(0) + 1/2(5) + 0(0) + 1/2(0) + 0(0) = 4
note that for this mask we will need to put the result in the pixel location corresponding to the lower right corner, since there is no center pixel.
The above methods will only to enlarge an image by a factor of (2N -1), but what if we want to enlarge an image by something other than a factor of (2N - I)?
This is done by defining an enlargement number K, then following this process:
140 - 125=15.
The two pixel values between the 125 and 140 are :
125 + 5 = 130 and 125 + 2 x 5 = 135
Two other operations of interest for the ROI image geometry are translation and rotation.
where r\' and c\' are the new coordinate, r and c are the original coordinates and ro and co are the distances to move, or translate ,the image.
The rotation and translation process can be combined into 1 set of equations: