CODEWITHSUNDEEP
pythonnumpypyqt5
vanderub
vanderub

Reputation: 57

PyQt5 set RGBA pixel in numpy array

i'm struggling to set pixels to a specific RGBA value with a numpy array. Im using the QImage.Format_RGBA8888.

When i'm doing it with QImage.Format_RGB888 it makes what i want, but i'd like to have transparency.

I'm not sure What i'm overlooking?

Thanks for any advice :)

import sys
from PyQt5 import QtWidgets as qw
from PyQt5 import QtGui as qg
from PyQt5 import QtCore as qc
import numpy as np


class MainWindow(qw.QMainWindow):
    def __init__(self):
        super(qw.QMainWindow, self).__init__()
        self.height = 500
        self.width = 500
        self.setWindowTitle("V.0.0")
        self.setMinimumSize(self.width, self.height)

        # display
        self.display = qw.QLabel()
        self.setCentralWidget(self.display)
        # self.display.setGeometry(qc.QRect(0, 0, self.width, self.height))

        self.background()

        self.display.setPixmap(qg.QPixmap.fromImage(self.world_img))

        self.show()

    def background(self):
        self.world = np.zeros([self.width, self.height, 4], dtype=np.uint8)
        self.world += 255 # should do all black?
        self.world[20, 30, :] = [135, 23, 53, 1]
        self.world[21, 31, :] = [135, 23, 53, 1]
        self.world[22, 32, :] = [135, 23, 53, 1]
        self.world_img = qg.QImage(self.world, self.width, self.height, qg.QImage.Format_RGBA8888)


# Start app
if __name__ == '__main__':
    app = qw.QApplication(sys.argv)
    Game = MainWindow()
    sys.exit(app.exec_())

Upvotes: 1

Views: 654

Answers (1)

NateTheGrate
NateTheGrate

Reputation: 600

You have the right idea!

The thing you're missing is that RGB values of 255,255,255 is white, not black. As well, the transparency "A" axis goes from 0 - 255, where 0 is opaque and 255 is completely transparent.

Examples:

  • If the RGBA values are (255,255,255,0), then you will see black. This is because the transparency is set to 0.
  • If the RGBA values are (255,255,255,255), then you will see white.
  • If the RGBA values are (135, 23, 53, 255), then you'll see dark red (your example in the code.)

Small thing for visibility, consider setting a test patch rather than a test pixel, like so:

self.world[20:40, 30:50, :] = [135, 23, 53, 128]

Upvotes: 3

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