Image_processing module

class Image_processing.Image(file_name=None, file_ext=None, color_type=None, image_array=None, dimensions=None, contrast_stretch_array=None, hist_eq_array=None, rev_video_array=None, image_as_string=None, log_comp_array=None, max_intensity_val=None, alpha_channel='no')

contrast_stretch()

Carries out contrast stretching on input image

Returns:self.contrast_stretch_array - numpy array containing image

data of altered image :returns: run_time - the time it took to run this method in seconds

decode_string()

Takes in base64 string containing image data, determines the file type (either PNG or JPEG) based off this info, then saves the image to disc under the name ‘working_image’ with the same file extension as the input file

gather_data()

Gathers useful information about an input image and stores the data as object attributes. Functions by taking in a base64 string, decoding it then saving it as a numpy array

Returns:self.color_type a string stating ‘greyscale’ or ‘color’ Returns:self.dimensions an array in the form of (rows, columns) Returns:self.image_array: a numpy array containing the digital

image data :returns: self.alpha_channel: a yes or no string indicating whether the image contains an alpha channel

get_file_ext()

Reads base64 image data and determines image file type ( PNG/JPEG)

Returns:self.file_ext - string reading either ‘.JPEG’ or ‘.PNG’

hist_eq()

Carries out histogram equalization on input image

Returns:self.hist_eq_array - numpy array containing image data of

altered image :returns: run_time - the time it took to run this method in seconds

log_compression()

Carries out logarithmic compression on input image

Returns:self.log_comp_array - numpy array containing image

data of altered image :returns: run_time - the time it took to run this method in seconds

output_histogram_data(hist_type)

Outputs image histogram data as arrays

Parameters:hist_type – the type of data for which the histogram is being

produced (‘orignal’ - unaltered image, ‘hist_eq’ - image altered by histogram equalization, ‘rev_vid’ - image altered by reverse video, ‘contrast_stretch’ - image altered by contrast stretching, ‘log_comp’ - image altered by logarithmic compression :returns: red_hist - the red frequency values of the image’s histogram :returns: blue_hist-the blue frequency values of the image’s histogram :returns: green_hist - the green frequency values of the image’s histogram :returns: x_vals - the intensity values of the image (0-255)

remove_alpha_channel()

Removes alpha channel from image data array

Returns:self.image_array - image data array with alpha channel

values removed

reverse_video()

Carries out reverse video on input image

Returns:self.rev_video_array - numpy array containing image

data of altered image :return: run_time - the time it took to run this method in seconds

show_histogram()

Generates histogram of image in Python

Image_processing.contrast_stretching_complete(image_string)

Takes in base64 string, initializes an instance of Image class using this data, carries out contrast stretching, and generates plottable histogram data

Parameters:image_string – base64 string containing image data Returns:red_his - the red frequency values of the image’s histogram Returns:blue_hist - the blue frequency values of the image’s histogram Returns:green_hist - the green frequency values of the image’s histogram Returns:x_vals - the intensity values of the image (0-255) for histogram Returns:base64_string - string containing data for altered image Returns:run_time - the time it took to run the contrast stretching

algorithm in seconds

Image_processing.encode_string(filename, file_ext)

Encodes image saved on disc into a base64 string

Parameters:

• filename – filename of image on disc which is to be encoded
• file_ext – file extension of filename (.PNG/.JPEG)

Returns:

string - base64 encoded image string

Image_processing.histogram_data(image_string)

Takes in base64 string, initializes an instance of Image class using this data, and generates plottable histogram data

Parameters:image_string – base64 string containing image data Returns:red_hist - the red frequency values of the image’s histogram Returns:blue_hist - the blue frequency values of the image’s histogram Returns:green_hist - the green frequency values of the image’s histogram Returns:x_vals - the intensity values of the image (0-255) for histogram

Image_processing.histogram_eq_complete(image_string)

Takes in base64 string, initializes an instance of Image class using this data, carries out histogram equalization, and generates plottable histogram data

Parameters:image_string – base64 string containing image data Returns:image - instance of Image class

Image_processing.initialize_image(image_string)

Creates instance of Image class called ‘image’ with the input base64 string as the image_as_string attribute

Parameters:image_string – base64 string containing image data Returns:image - instance of Image class

Image_processing.log_compression_complete(image_string)

Takes in base64 string, initializes an instance of Image class using this data, carries out logarithmic compression, and generates plottable histogram data

Parameters:image_string – base64 string containing image data Returns:red_hist - the red frequency values of the image’s histogram Returns:blue_hist - the blue frequency values of the image’s histogram Returns:green_hist - the green frequency values of the image’s histogram Returns:x_vals - the intensity values of the image (0-255) for histogram Returns:base64_string - string containing data for altered image Returns:run_time - the time it took to run the log compression algorithm

algorithm in seconds

Image_processing.output_altered_histogram_data(hist_type, file_ext)

Outputs arrays containing histogram data of altered images

Parameters:

• hist_type – the type of data for which the histogram is being produced (‘orignal’ - unaltered image, ‘hist_eq’ - image altered by histogram equalization, ‘rev_vid’ - image altered by reverse video, ‘contrast_stretch’ - image altered by contrast stretching, ‘log_comp’ - image altered by logarithmic compression
• file_ext – file extension of filename (.PNG/.JPEG)

Returns:

red_hist - the red frequency values of the image’s histogram

Returns:

blue_hist - the blue frequency values of the image’s histogram

Returns:

green_hist - the green frequency values of the image’s histogram

Returns:

x_vals - the intensity values of the image (0-255)

Image_processing.reverse_video_complete(image_string)

Takes in base64 string, initializes an instance of Image class using this data, carries out reverse video, and generates plottable histogram data

Parameters:image_string – base64 string containing image data Returns:red_hist - the red frequency values of the image’s histogram Returns:blue_hist - the blue frequency values of the image’s histogram Returns:green_hist - the green frequency values of the image’s histogram Returns:x_vals - the intensity values of the image (0-255) for histogram Returns:base64_string - string containing data for altered image Returns:run_time - the time it took to run the reverse video

algorithm in seconds