##Writeup

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Advanced Lane Finding Project

The goals / steps of this project are the following:

• Compute the camera calibration matrix and distortion coefficients given a set of chessboard images.
• Apply a distortion correction to raw images.
• Use color transforms, gradients, etc., to create a thresholded binary image.
• Apply a perspective transform to rectify binary image ("birds-eye view").
• Detect lane pixels and fit to find the lane boundary.
• Determine the curvature of the lane and vehicle position with respect to center.
• Warp the detected lane boundaries back onto the original image.
• Output visual display of the lane boundaries and numerical estimation of lane curvature and vehicle position.

Rubric Points

###Here I will consider the rubric points individually and describe how I addressed each point in my implementation.

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###Writeup / README

###Camera Calibration

####1. Briefly state how you computed the camera matrix and distortion coefficients. Provide an example of a distortion corrected calibration image.

The code for this step is contained in the first code cell of the IPython notebook located in "./examples/example.ipynb" (or in the file called calibration.py).

I start by preparing "object points", which will be the (x, y, z) coordinates of the chessboard corners in the world. Here I am assuming the chessboard is fixed on the (x, y) plane at z=0, such that the object points are the same for each calibration image. Thus, objp is just a replicated array of coordinates, and objpoints will be appended with a copy of it every time I successfully detect all chessboard corners in a test image. imgpoints will be appended with the (x, y) pixel position of each of the corners in the image plane with each successful chessboard detection.

I then used the output objpoints and imgpoints to compute the camera calibration and distortion coefficients using the cv2.calibrateCamera() function. I applied this distortion correction to the test image using the cv2.undistort() function and obtained this result:

###Pipeline (single images)

####1. Provide an example of a distortion-corrected image. To demonstrate this step, I will describe how I apply the distortion correction to one of the test images like this one:

For distorting I use undistort function from OpenCV and mtx+dist values from camera calibratin.

####2. Describe how (and identify where in your code) you used color transforms, gradients or other methods to create a thresholded binary image. Provide an example of a binary image result. I used a combination of color and gradient thresholds to generate a binary image (thresholding steps at lines # Candy and color processing # in solution.py). Here's an example of my output for this step.

In additional I applyed Gaussian blur and region of interest:

####3. Describe how (and identify where in your code) you performed a perspective transform and provide an example of a transformed image.

The code for my perspective transform includes a function called warper(), which appears in define_warper() funtion in the file solution.py. The warper() function takes as inputs an image (img), as well as source (src) and destination (dst) points. I chose the hardcode the source and destination points in the following manner:

    src = np.float32([
        [255, 685],
        [1050, 685],
        [590, 455],
        [695, 455]
    ])

    dst = np.float32([
        [320, 685],
        [950, 685],
        [320, 0],
        [950, 0]
    ])

This resulted in the following source and destination points:

Source	Destination
255, 685	320, 685
1050, 685	950, 685
590, 455	320, 0
695, 455	950, 0

I verified that my perspective transform was working as expected by drawing the src and dst points onto a test image and its warped counterpart to verify that the lines appear parallel in the warped image.

####4. Describe how (and identify where in your code) you identified lane-line pixels and fit their positions with a polynomial?

Then I used histogram (peaks_histogram() functon in solution.py) to define lane points and then fit my lane lines with a 2nd order polynomial (curvature() function in solution.py) kinda like this:

####5. Describe how (and identify where in your code) you calculated the radius of curvature of the lane and the position of the vehicle with respect to center.

I did this in curvature() function in my code in solution.py

####6. Provide an example image of your result plotted back down onto the road such that the lane area is identified clearly.

I implemented this step in my code in solution.py in the function fillPoly(). Here is an example of my result on a test image:

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###Pipeline (video)

####1. Provide a link to your final video output. Your pipeline should perform reasonably well on the entire project video (wobbly lines are ok but no catastrophic failures that would cause the car to drive off the road!).

Here's a link to my video result

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###Discussion

####1. Briefly discuss any problems / issues you faced in your implementation of this project. Where will your pipeline likely fail? What could you do to make it more robust?

The biggest issue I faced in my implementation of this project is finding Lane points in the case with curved dotted lines. The first trick here is not to skip the whole frame but points with unexpected coordinates:

if abs(p1-p01)>200: continue

The second trick is to regenerated y coordinates and then recalculated x values:

yvals = np.arange(h - h / 2, h, 1.0)
lane.polyfit[0] * yvals ** 2 + lane.polyfit[1] * yvals + lane.polyfit[2]

Further improvement:

• Use smoothing with previous measurements
• Control minimum and maximum wide of lane