[PYTHON] Learn with Pixel 4 camera Depth map-1 (helper implementation)


This article cuts out only the Code part handled in the article serialized in Note. If you are interested in the technical background, please refer to the Note article.

implementation of helper

Since I / O of images is used a lot, I will implement them together as a helper. Doing so will make the Code easier to read and easier to maintain. The library to be used is as follows. Please install it with pip etc. in advance.

Let's describe the actual implementation.

Create a list of files in the specified Folder

Use glob to create an absolute path list of files with the specified extension in the specified Folder. You can use a relative bus, but since the absolute path is easier to handle later, you will get it with the absolute path.


def make_file_path_list(path: str, ext: str) -> [str]:
    """ Make file path list from path and ext information
    path :str
     project path
    ext :str
     specific the file extention in order to make path list

    file path list :[str]
     list of file path under the path with the specialied extention
    path_str = path + '*.' + ext
    return glob.glob(path_str)

Next, read the image data based on the obtained list of absolute paths. If it is a PGM file, it does not make much sense, but as a convention, change the RGB sequence. Since OpenCV is read by BGR with Defalt setting, it is set to RGB to maintain consistency with other processing.


def read_img_from_path(filepath: [str], width: int, height: int):
    """ Read image file from path list
    filepath :[str]
     File list for image reading
    width :int
     Output image width
    height: int
     Output iamge height

     Return the read image data as RGB format
    stocker = []
    for path in filepath:
        img = cv2.imread(path)
        img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
        img = cv2.resize(img, dsize=(width, height), interpolation = cv2.INTER_CUBIC)

    return stocker

Let's implement the exporter here as well. The path list to write to, the image data, and the output Format are specified as arguments. If nothing is specified, it will be output in JPEG format.


def write_img_to_path(outpath: str, filepaths: [str], imgs: [np.ndarray], ext: str='jpg'):
    """ write images to path list
    outpath: str
     ouput path
    filepath: [str]
     file path list for file saving
    imgs: [np.ndarray]
     image data
    ext: str
     file format and define extention
    for idx, filepath in enumerate(filepaths):
        # extract file name
        filename = filepath.split('/')[-1]; filename = filename.split('.')[0]

        # make output file path from filename and extention 
        output_file_path = outpath + filename + '.' + ext

        # output images
        cv2.imwrite(output_file_path, imgs[idx])

Later, since it is necessary to judge whether it is a Left image or a Right image, implement a function that cuts out the Left or Right from the image file name and judges it. If it is a Left image, it returns True, and if it is Right, it returns False.


def loc_detector_from_name(file_name: str) -> bool:
    """ Split location information from file name and return location info
    file_name: str
     file name which includes location info such as 'left' or 'right'
    loc: bool
     return location info as boolian, True: 'left', False: 'right'
    loc = file_name.split('_')[-1]; loc = loc.split('.')[0]
    if loc == 'left':
        return True
    return False

Later, image processing will standardize the pixel values ​​in the range of 0.0 to 1.0, so define a function for that as well.


def normarize_img_data(img: np.ndarray, max_value: int = 255):
    """ Normarize image data, find min_value and max_value, and normarize
    img: np.ndarray
     original image data
    max_value: int
     define maximum value after normarization

    # get min, max and range for normarization
    min_value = img.min()
    max_value = img.max()
    value_range = max_value - min_value

    # normalized image
    norm_img = (img - min_value) / value_range * max_value

    # return
    return norm_img.astype(np.uint8)

This is the end of halper preparation.

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