tkinter example tkinter png (snippet)

Python tkinter (gui) example 'tkinter png'

Modules used in program:

• import png

tkinter png

Python tkinter example: tkinter png

#!/usr/bin/env python3
# tkinter-png - example of using tkinter and pypng to display pngs (albeit reduced quality)
# in nothing but pure python. Can use RGBA images, but alpha is opaque or transparent only.
# v0.75 - Example code and module seperated out, speed optimisation of the convert function

from array import *
from tkinter import *
import png

## tkinter hacking section ##

# Define our new tkinter.PhotoImage functions and override the stock version
class PhotoImage(PhotoImage):
    def transGet(self, x, y):
        """Returns a boolean if pixel at (x,y) is transparent"""
        return self.tk.call(self.name, "transparency", "get", x, y)

    def transSet(self, x, y, alpha):
        """Makes the pixel at (x,y) transparent if alpha is is true or opaque otherwise"""
        self.tk.call(self.name, "transparency", "set", x, y, alpha)

    # tkinter already has a gimped version of copy, but it's pretty useless
    # this version is still lacking and doesn't have all options, but is actually usable
    def copy(self, sourceImage, fromBox=None, toBox=None):
        """Copies from region of sourceImage at fromBox to current image at toBox"""
        args = (self.name, "copy", sourceImage)
        if fromBox:
            if fromBox[0] == "-from":
                fromBox = fromBox[1:]
            args = args + ("-from",) + tuple(fromBox)
        if toBox:
            if toBox[0] == "-to":
                toBox = toBox[1:]
            args = args + ("-to",) + tuple(toBox)
        self.tk.call(args)

    def redither(self):
        """Recalculate dithering used in PhotoImages to fix errors that may occur if image data was supplied in chunks"""
        self.tk.call(self.name, "redither")

    def data(self, bg=None, fromBox=None, grey=None):
        """Returns image data in the form of a string"""
        args = (self.name, "data")
        if bg:
            if bg[0] == "-background":
                bg = bg[1:]
            args = args + ("-background",) + tuple(bg)
        if fromBox:
            if fromBox[0] == "-from":
                fromBox = fromBox[1:]
            args = args + ("-from",) + tuple(fromBox)
        if grey:
            if grey == True or grey == "-grayscale":
                args = args + ("-grayscale",)


## PngImageTk section ##

class PngImageTk(object):
    """A png image loaded and placed into a tkinter.PhotoImage object"""
    def __init__(self, filename):
        # Read image, create list of pixel RGB or RGBA values
        r = png.Reader(filename)
        # Try to use RGB8 load if no alpha chanel otherwise use alpha (RGBA8)
        try:
            self.w, self.h, self.pixels, self.meta = r.asRGB8()
        except:
            self.w, self.h, self.pixels, self.meta = r.asRGBA8()
        self.pixeldata = list(self.pixels) #pixeldata has each row of the image as an array
        self.x = 0
        self.y = 0
        self.image = PhotoImage(width=self.w, height=self.h) #use photoimage as temporary oject to write to canvas

    # Print meta data for image
    def __str__(self):
        rep = "Width:", self.w, "\n"
        rep += "Height:", self.h, "\n"
        rep += "Bitdepth:", self.meta["bitdepth"], "\n"
        rep += "Greyscale:", self.meta["greyscale"], "\n"
        rep += "Alpha:", self.meta["alpha"], "\n"
        return rep

    # Used to split each row into pairs of RGB or RGBA values
    def chunks(self, l, n):
        return [l[i:i+n] for i in range(0, len(l), n)]

    # Convert pixeldata into a PhotoImage object
    def convert(self):
        alphapixels = []
        if self.meta["alpha"] == True:
            values = 4
            a_append = alphapixels.append
        else:
            values = 3

        pixelrows = []

        # Possible optimisation by minimising re-evaluation of dot notation in loops
        p_append = pixelrows.append
        pixeldata = self.pixeldata
        chunks = self.chunks
        alpha = self.meta["alpha"]
        x = self.x
        y = self.y
        w = self.w
        h = self.h
        put = self.image.put
        transSet = self.image.transSet

        for row in pixeldata:
            row = row.tolist() #convert from array to list
            chunked = chunks(row, values) #RGB/RGBA format = 3/4 values

            for item in chunked:
                if alpha == True:
                    # if 100% transparent, remember this pixel so we can make it transparent later
                    if item[3] == 0:
                        a_append((x, y))
                    del item[-1] #remove alpha bit

                    # Increment position, used for tracking coordinates of transparent pixels
                    x += 1
                    if x == w:
                        y += 1
                        x = 0

            p_append(["#%02x%02x%02x" % tuple(item) for item in chunked])

        pixelrows = tuple(tuple(x) for x in pixelrows) #convert our list of lists into a tuple of tuples
        put(pixelrows,(0,0, w,h)) #pixels are finally written to the PhotoImage

        # If we have alphapixels, set each stored coordinate to transparent
        if alphapixels:
            for item in alphapixels:
                transSet(item[0],item[1], "True")

Useful links

• Learn Tkinter: https://pythonbasics.org/tkinter/
• Wikipedia tkinter: https://en.wikipedia.org/wiki/Tkinter