DEV Community: Onelinerhub

Using Pillow module to draw figures with Python

Onelinerhub — Thu, 10 Nov 2022 08:57:55 +0000

1. How to draw a line

from PIL import Image, ImageDraw

im = Image.new("RGB", (400, 300))  
dr = ImageDraw.Draw(im)
dr.line([(50,200), (350,200)], fill ="white", width = 5)
im.show()

ImageDraw.Draw - create drawing object,
.line( - draws a line,
(50,200), (350,200) - starting and ending coordinates of a line.

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2. How to draw a point

from PIL import Image, ImageDraw

im = Image.new("RGB", (400, 300))  
dr = ImageDraw.Draw(im)
dr.point((50,50), fill="white")
im.show()

.point( - draws a single point,
(50,50) - point coordinates.

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3. How to draw a triangle

from PIL import Image, ImageDraw

im = Image.new("RGB", (400, 300))  
dr = ImageDraw.Draw(im)
dr.polygon([(50,50), (350,150), (200, 250)], outline="white")
im.show()

.polygon( - draws polygon from given coordinates (with any number of dots),
(50,50), (350,150), (200, 250) - triangle dots coordinates.

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4. How to draw an arc

from PIL import Image, ImageDraw

im = Image.new("RGB", (400, 300))  
dr = ImageDraw.Draw(im)
dr.arc([(50,50), (350,250)], start = 20, end = 230, fill ="white")
im.show()

.arc( - draws an arc,
(50,50), (350,250) - coordinates of an arc bounding rectangle,
start = 20 - starting angle (starts from 3pm),
end = 230 - ending angle.

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5. How to draw an ellipse

from PIL import Image, ImageDraw

im = Image.new("RGB", (400, 300))  
dr = ImageDraw.Draw(im)
dr.ellipse([(50,50), (350,250)], outline ="white")
im.show()

.ellipse( - draws an ellipse,
(50,50), (350,250) - bounding rectangle to fit ellipse into.

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6. How to draw rectangle

from PIL import Image, ImageDraw

im = Image.new("RGB", (400, 300))  
dr = ImageDraw.Draw(im)
dr.rectangle([(50,50), (350,250)], outline="white")
im.show()

.rectangle( - draws rectangle,
(50,50), (350,250) - rectangle top left and bottom right points coordinates.

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8 Python chart examples using Matplotlib

Onelinerhub — Thu, 03 Nov 2022 11:01:22 +0000

1. 3D Scatter chart

import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(projection='3d')

ax.scatter(1, 1, 1)
ax.scatter(2, 2, 1)
ax.scatter(2, 3, 0)

plt.show()

Where projection='3d' is used to set 3d mode for this chart, .scatter( plots a point chart.

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2. Table

Well, this is not a chart, but tables are still used sometimes.

import matplotlib.pyplot as plt

data = [[1, 2, 3, 4, 5],
        [10,20,30,40,50],
        [11,21,31,41,51]]

plt.table(data, loc='center', colLabels=['A','B','C','D','E'])

plt.show()

Here data is the data to use for table cells. Then we call .table( to plot a table and colLabels to define column titles.

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3. Boxplot chart

import matplotlib.pyplot as plt

plt.boxplot([2,3,6,2,4,5,1,10])

plt.show()

We just use .boxplot( to plot boxplot chart.

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4. Line chart

import matplotlib.pyplot as plt
plt.plot([1,2,10,6,15,3,4])
plt.show()

The .plot( is used to plot a line based on given data.

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5. Bar chart

import matplotlib.pyplot as plt
plt.bar(['UA', 'UK', 'USA'], [10, 11, 12])
plt.show()

The .bar method will plot bar chart, while ['UA', 'UK', 'USA'] is used as x-axis values and [10, 11, 12] as y-axis values.

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6. Heatmap

import matplotlib.pyplot as plt

fig, ax = plt.subplots()
im = ax.imshow([[0.8, 2.4, 2.5], [1.3, 1.2, 0.0], [0.1, 2.0, 0.0]])

plt.show()

To draw heatmap we use .imshow(, which displays given data as an image.

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7. Histogram

import matplotlib.pyplot as plt

x = [1,2,5,1,2,3,5,6,7,4,2,2,4,5,6]
plt.hist(x,bins=5)
plt.show()

To build a histogram we use .hist( and set bins - number of histogram bins (bars) to group data into.

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8. World map

import matplotlib.pyplot as plt
import geopandas

world = geopandas.read_file(geopandas.datasets.get_path('naturalearth_lowres'))
world.plot()
plt.show()

First, we load geopandas - module to work with maps and geo charts. Then world.plot()` can be used to plot world map.

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Resizing & cropping images using Python Pillow

Onelinerhub — Thu, 27 Oct 2022 12:21:43 +0000

We're going to use Image and ImageOps components of Pillow module to resize/crop image.

How to resize an image keeping aspect ratio

from PIL import Image, ImageOps

im = Image.open('/var/www/examples/heroine.png')
width = 100
height = width * im.size[1]/im.size[0]

im = im.resize((width, height))

100 - resized image width,
width * im.size[1]/im.size[0] - calculates height so that aspect ratio is maintained.

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How to crop an image from center

im = Image.open('/var/www/examples/heroine.png')
crop = (400, 400)
left = round((im.size[0] - crop[0])/2)
top = round((im.size[1] - crop[1])/2)
im = im.crop((left, top, crop[0]+left, crop[1] + top))

(400, 400) - cropping area width and height,
(im.size[0] - crop[0])/2` - left coordinate of a crop area to position in the horizontal center,
(im.size[1] - crop[1])/2` - top coordinate of a crop area to position in the vertical center.

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How to resize/crop an image cropped to fit certain area (cover thumbnail)

im = Image.open('/var/www/examples/heroine.png')
im = ImageOps.fit(im, (100,100), Image.ANTIALIAS)

100,100 - thumbnail area width and height,
ImageOps.fit( - fits an image into given area.

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5 examples of using Pillow to manipulate images in Python

Onelinerhub — Thu, 20 Oct 2022 10:09:41 +0000

1. How to automatically tune image contrast

from PIL import Image, ImageOps

im = Image.open('/var/www/examples/heroine.png')

im = ImageOps.autocontrast(im, cutoff = 5)
im.show()

ImageOps.autocontrast - set contrast automatically based on given cutoff,
cutoff = 5 - defines part of histogram (in percents) that should be removed,

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2. How to convert an image to a black-and-white color scheme

from PIL import Image, ImageFilter

im = Image.open('/var/www/examples/heroine.png')
im = im.convert('1')

im.show()

.convert('1') - convert image to black and white colors,

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3. How to load an image over internet

from PIL import Image
import requests
from io import BytesIO

url = 'https://examples.onelinerhub.com/heroine.png'

response = requests.get(url)
img = Image.open(BytesIO(response.content))

im.show()

requests.get - loads data from given url,
response.content - get content previously loaded from url,

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4. How to rotate an image without cropping it

from PIL import Image, ImageEnhance

im = Image.open('/var/www/examples/heroine.png')
im = im.rotate(90, expand=True)

im.show()

expand=True - increase image size instead of cropping while rotating,

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5. How to add rotated text to an image

The idea here is to create 2 images - one to add text to and another with the text itself. This way we can rotate second image and merge them to get desired effect.

from PIL import Image, ImageDraw, ImageFont

im = Image.open('/var/www/examples/heroine.png')
text = "I am hero"

tim = Image.new('RGBA', (500,200), (0,0,0,0))
dr = ImageDraw.Draw(tim)
ft = ImageFont.truetype('/var/www/examples/roboto.ttf', 100)
dr.text((0, 0), text, font=ft, fill=(200, 200, 0))

tim = tim.rotate(30,  expand=1)

im.paste(tim, (0,0), tim)
im.show()

.text( - draws text with given params,
.rotate( - rotate given image,
.paste( - paste image with text on top of loaded image,

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5 more advanced GD examples to manipulate images with PHP

Onelinerhub — Thu, 13 Oct 2022 10:57:56 +0000

1. How to draw pie chart

<?php

$data = [50, 90, 150, 360];

$im = imagecreatetruecolor(400, 300);
$c_black = imageColorAllocate($im, 0,0,0);

foreach ( $data as $i => $v ) {
  $c = imageColorAllocate(
    $im, 46 + $i * 30,204 - $i * 30, 64 + $i * 30
  );
  imagefilledarc(
    $im, 200, 150,
    100 + $i * 10, 100 + $i * 10, $i ? $data[$i-1] : 0,
    $v, $c, IMG_ARC_PIE
  );
}

imagePng($im, '/tmp/image.png');

$data - sample data to draw pie chart based on,
imagecreatetruecolor - creates true color GD image object with specified width & height,
imageColorAllocate - creates color object to use for pie (we use $i value to randomize color),
imagefilledarc - draw next pie,
200, 150 - pie center coordinates,
imagePng - saves image in PNG format to the given path.

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2. How to flip an image

<?php

$file = '/var/www/examples/heroine.png';
$im = imagecreatefrompng($file);

imageflip( $im, IMG_FLIP_VERTICAL );
imagePng($im, '/tmp/image.png');

$file - image to rotate,
imagecreatefrompng - creates GD image object from given PNG image,
imageflip - flips given image in a specified direction,
IMG_FLIP_VERTICAL - flips image vertically, explore other options,
imagePng - saves image in PNG format to the given path.

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3. How to get pixel color

$file = '/var/www/examples/heroine.png';
$im = imagecreatefrompng($file);
$c = imagecolorat($im, 100, 100);
list($r, $g, $b) = [($c >> 16) & 0xFF, ($c >> 8) & 0xFF, $c & 0xFF];

$file - sample image to work with,
imagecreatefrompng - creates GD image object from given PNG image,
imagecolorat - returns color at a given position as an integer,
100, 100 - we're getting color on 100 pixels from top and 100 pixels from left,
$r, $g, $b - variables will contain decoded values for R, G and B color channels.

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4. How to rotate an image

<?php

$file = '/var/www/examples/heroine.png';
$im = imagecreatefrompng($file);

$c_black = imageColorAllocate($im, 0,0,0);
$imr = imagerotate( $im, 90, $c_black );

imagePng($imr, '/tmp/image.png');

$file - image to rotate,
imagecreatefrompng - creates GD image object from given PNG image,
imageColorAllocate - creates color object to later use in image,
imagerotate - rotates given image and returns new gd image object,
90 - rotate image by 90 degrees,
$c_black - color to use for background (if necessary),
imagePng - saves image in PNG format to the given path.

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5. How to set line thickness

<?php

$im = imagecreatetruecolor(400, 300);

$c_black = imageColorAllocate($im, 0,0,0);
$c_green = imageColorAllocate($im, 46,204,64);

for ( $thick = 5; $thick > 0; $thick-- ) {
  imageline($im, 50, 50 + $thick, 350, 250 + $thick, $c_green);
}


imagePng($im, '/tmp/image.png');

imagecreatetruecolor - creates true color GD image object with specified width & height,
imageColorAllocate - creates color object to later use in image,
imageline - draws line using given coordinates and color,
$thick = 5 - resulting line thickness (5 in our case),
imagePng - saves image in PNG format to the given path.

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How to add watermark to image using php gd

Onelinerhub — Thu, 06 Oct 2022 15:07:31 +0000

Using PHP GD library to adding watermark is as simple as merging 2 images.

First, we create gd image from photo to add watermark to:

$bg = imagecreatefromjpeg('photo.jpg');

Next, we create gd image from watermark file (logo.png) and get it's size:

$wm = imagecreatefrompng('logo.png');
$wm_size = getimagesize('logo.png');

Now place watermark at 25 pixels from top & left borders:

imagecopy($bg, $wm, 25, 25, 0, 0, $wm_size[0], $wm_size[1]);

Finally, save resulting JPG image to result.jpg:

imagejpeg($bg, 'result.jpg');

Get and contribute more PHP GD code solutions.

Compacting historical data in Clickhouse

Onelinerhub — Wed, 05 Oct 2022 15:54:55 +0000

In most cases you need full details on your data collected, so you don’t want to compact (store aggregated) your data. But there are plenty of cases, when you actually need only recent data in full perspective and historical data can be easily compacted.

E.g. you will only want to save, say, last month of collected user events in event-per-row form. But older data is fine to keep aggregated in total events per day format.

This can save space and reduce query execution times. Clickhouse can manage this automatically, let’s see how.

Aligning text horizontally and vertically with PHP GD

Onelinerhub — Thu, 08 Sep 2022 14:14:49 +0000

Let's draw text on 400x300 image as example.

Horizontal center align

$im = imagecreatetruecolor(400, 300);

$c_black = imageColorAllocate($im, 0,0,0);
$c_green = imageColorAllocate($im, 46,204,64);
$text = 'Hi';

$font = '/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf';
$p = imagettfbbox(40, 0, $font, $text);

imagettftext($im, 40, 0, (400 - $p[2])/2, 100, $c_green, $font, $text);
imagePng($im, '/tmp/image.png');

We use (400 - $p[2])/2 to calculate x coordinate so our text is centered horizontally. Open original or edit on Github.

Vertical and horizontal center align

$im = imagecreatetruecolor(400, 300);

$c_black = imageColorAllocate($im, 0,0,0);
$c_green = imageColorAllocate($im, 46,204,64);
$text = 'Hi';

$font = '/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf';
$p = imagettfbbox(40, 0, $font, $text);

imagettftext($im, 40, 0, (400 - $p[2])/2, (300 - $p[5])/2, $c_green, $font, $text);
imagePng($im, '/tmp/image.png');

We've used (400 - $p[2])/2to center align text horizontally and(300- $p[5])/2 to get y coordinate so our text is also centered vertically.

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3 hacks when resizing images with GD in PHP

Onelinerhub — Wed, 31 Aug 2022 14:46:20 +0000

1. Better antialiasing with GD based on resampling

GD has shitty antialiasing implementation, but this can be quickly fixed with a simple hack:

<?php

$im = imagecreatetruecolor(4000, 3000);
imageantialias($im, true);

$c_black = imageColorAllocate($im, 0,0,0);
$c_green = imageColorAllocate($im, 46,204,64);

imagefilledellipse($im, 2000, 1500, 800, 800, $c_green);

$imf = imagecreatetruecolor(400, 300);
imagecopyresampled($imf, $im, 0,0,0,0, 400,300,4000,3000);

imagePng($imf, '/tmp/image.png');

4000, 3000 - we have created initial image of large size (10x what we need in result),
imagecopyresampled - now we resize source large image (4000x3000) to resulting image (400x300) to apply better antialiasing.

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2. Resize an image proportionally

<?php

$file = '/var/www/examples/heroine.png';
$size = getimagesize($file);
$im = imagecreatefrompng($file);

$w = 400;
$h = $w * $size[1] / $size[0];

$imf = imagecreatetruecolor($w, $h);
imagecopyresampled($imf, $im, 0,0,0,0, $w,$h,$size[0],$size[1]);

imagePng($imf, '/tmp/image.png');

$w = 400 - resize image to 400 pixels wide,
$w * $size[1] / $size[0] - calculates resized image height based on source image proportions.

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3. Resize transparent PNG image

<?php

$file = '/var/www/examples/clouds.png';
$size = getimagesize($file);
$im = imagecreatefrompng($file);

$w = 300;
$h = $w * $size[1] / $size[0];

$imf = imagecreatetruecolor($w, $h);
imagealphablending($imf, false);
imagesavealpha($imf, true);
imagecopyresampled($imf, $im, 0,0,0,0, $w,$h,$size[0],$size[1]);

imagePng($imf, '/tmp/image.png');

imagealphablending - we're disabling alpha blending to prevent transparent background being converted to black color,
imagesavealpha - we're enabling alpha channel (controls transparency) for resulting image.

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10 Useful vim commands for coders

Onelinerhub — Thu, 25 Aug 2022 14:23:42 +0000

You need to be in command mode (pres Esc for that) to use these commands.

1. Add a new line

Press o (small) to add new line below cursor, or O (big) to add new line above cursor.

2. Comment multiple lines

Press Ctrl + v
Select lines with arrows keys
Press Shift + i
Input commenting symbol(s) (e.g. "//")
Press Esc

3. Delete line

Press dd to delete current line.

4. Delete word

Press dw to delete current word (cursor should be placed at the beginning of the word to delete).

5. Disable line wrap:

:set nowrap

6. Enable autoindent

:set smartindent

7. Go to the end of current line

Press $ to to the end of line.

8. Go to the end of file

:$

9. Go to specific line

E.g. to go to line number 51:

:51

10. Open file in a new tab

:tabnew <filename>

More useful Vim commands, add your commands on Github.

Creating Websocket servers and clients in Nodejs

Onelinerhub — Thu, 18 Aug 2022 16:11:25 +0000

1. Websocket server example

const WebSocketServer = require('ws');
const wss = new WebSocketServer.Server({ port: 8111 })

wss.on("connection", (ws,r) => {
  ws.on("message", data => {
    ws.send('You sent me: ' + data);
  });

  ws.on("close", () => { });
  ws.onerror = function () { };
});

require('ws') - import ws lib to create websocket server,
new WebSocketServer.Server - create and launch websocket server with params,
port: - port to listen on (in our case all network interfaces are going to be listened),
wss.on("connection" - what to do when someone connects to our server,
ws.on("message" - what to do when we've received a message from client,
ws.send( - send a message to client,
ws.on("close" - what to do when client closes connection,
ws.onerror - set custom error handler.

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2. Websocket client example

let ws = require('websocket');
let wsc = new ws.client;

wsc.on('connect', function(connection) {
  connection.sendUTF('Hello');

  connection.on('message', function(message) {
    console.log("Received: " + message.utf8Data);
    // connection.close();
  });
});

wsc.connect('ws://echoof.me:8111/');

require('websocket') - import websocket lib to create websocket client,
new ws.client - create new websocket client object,
wsc.on('connect' - specify what to do when client gets connected to websocket server,
connection.sendUTF - send message to server,
connection.on('message' - specify what to do when client received message from server,
connection.close() - close connection (and exit),
wsc.connect - connect to websocket server,
echoof.me:8111 - public echo websocket server.

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Reading and writing files in NodeJS

Onelinerhub — Thu, 11 Aug 2022 15:58:59 +0000

1. Reading file

const fs = require('fs');

fs.readFile("/tmp/test.txt", "utf8", (err, data) => {
  console.log(data);
});

fs.readFile( - reads file and returns data in callback function,
/tmp/test.txt - path to text file to read,
utf8 - encoding to read text in,
console.log(data) - log date from file to console.

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2. Writing file

const fs = require('fs');
fs.writeFile('/tmp/test.txt', 'hi!', (err, data) => {
  console.log(err);
});

require('fs') - library to work with file system,
/tmp/test.txt - path of file to write,
'hi!' - Data to write to file,
console.log(err) - if err is not null, something wrong happened,
fs.writeFile( - writes given data to specified file.

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