Our man in Marseille

Marcos Dione — Fri, 05 Aug 2016 13:51:35 GMT

Remember this?

For a few months now I've been trying to have a random slideshow of images. I used to do this either with kscreensaver, which for completely different reasons I can't use now, or xscreensavers' glslideshow, which, even when I compiled it by hand, I can't find the way to give it the root dir of the images. So, based on OMIT, I developed my own.

The differences with OMIT are minimal. It has to scan the whole tree for finding the appropriate files (its definition of "appropriate" could be improved, it's true); it goes into full screen mode with black background; and it (more) properly handles EXIF rotation¹. All that in 176 LOCs, including proper licensing (GPLv3), and developed in one day and refined the next one.

One interesting thing I found out is that pyexiv2 is deprecated, with is last release in 2011 (!!!). What this new app uses is its recommended replacement, gexiv2.

So, there you are. Like OMIT, it's in PyQt4, but this time in Python3 (that's why I used gexiv2 instead). Its TODO includes porting it to PyQt5 and a few other things. You can grab it here. I plan to do a proper release soon, but for the moment just drop it in your PATH and be happy with it.

http://www.daveperrett.com/articles/2012/07/28/exif-orientation-handling-is-a-ghetto/ ↩

Our man in Toulon

Marcos Dione — Wed, 27 Jan 2010 22:55:55 GMT

A couple of days ago Marcelo Fernández wrote a simple image viewer in PyGTK. It's less than 200 lines long¹, and I thought that it would be nice to compare how the same app would be written in PyKDE4. But then I though that it would not be fair, as KDE is a whole desktop environment and GTK is 'only' a widget library, so I did it in PyQt4 instead.

To make this even more fair, I hadn't had a good look at the code itself, I only run it to see what it looks like: a window with only the shown image in it, both scrollbars, no menu or statusbar, and no external file, so I assume he builds the ui 'by hand'. He mentions these features:

Pan the image with the mouse.
F1 to F5 handle the zoom from 'fit to window', 25%, 50%, 75% and 100%.
Zooming with the mouse wheel doesn't work.

Here's my take:

#! /usr/bin/python
# -*- coding: utf-8 -*-

# OurManInToulon - Example image viewer in PyQt4
# Marcos Dione <mdione@grulic.org.ar> - http://grulicueva.homelinux.net/~mdione/glob/

# TODO:
#     * add licence! (GPLv2 or later)

from PyQt4.QtGui import QApplication, QMainWindow, QGraphicsView, QGraphicsScene
from PyQt4.QtGui import QPixmap, QGraphicsPixmapItem, QAction, QKeySequence
import sys

class OMITGraphicsView (QGraphicsView):
    def __init__ (self, pixmap, scene, parent, *args):
        QGraphicsView.__init__ (self, scene)
        self.zoomLevel= 1.0
        self.win= parent
        self.img= pixmap
        self.setupActions ()

    def setupActions (self):
        # a factory to the right!
        zoomfit= QAction (self)
        zoomfit.setShortcuts ([QKeySequence.fromString ('F1')])
        zoomfit.triggered.connect (self.zoomfit)
        self.addAction (zoomfit)

        zoom25= QAction (self)
        zoom25.setShortcuts ([QKeySequence.fromString ('F2')])
        zoom25.triggered.connect (self.zoom25)
        self.addAction (zoom25)

        zoom50= QAction (self)
        zoom50.setShortcuts ([QKeySequence.fromString ('F3')])
        zoom50.triggered.connect (self.zoom50)
        self.addAction (zoom50)

        zoom75= QAction (self)
        zoom75.setShortcuts ([QKeySequence.fromString ('F4')])
        zoom75.triggered.connect (self.zoom75)
        self.addAction (zoom75)

        zoom100= QAction (self)
        zoom100.setShortcuts ([QKeySequence.fromString ('F5')])
        zoom100.triggered.connect (self.zoom100)
        self.addAction (zoom100)

    def zoomfit (self, *ignore):
        winSize= self.size ()
        imgSize= self.img.size ()
        print winSize, imgSize
        hZoom= 1.0*winSize.width  ()/imgSize.width  ()
        vZoom= 1.0*winSize.height ()/imgSize.height ()
        zoomLevel= min (hZoom, vZoom)
        print zoomLevel
        self.zoomTo (zoomLevel)

    def zoom25 (self, *ignore):
        self.zoomTo (0.25)

    def zoom50 (self, *ignore):
        self.zoomTo (0.5)

    def zoom75 (self, *ignore):
        self.zoomTo (0.75)

    def zoom100 (self, *ignore):
        self.zoomTo (1.0)

    def zoomTo (self, zoomLevel):
        scale= zoomLevel/self.zoomLevel
        print "scaling", scale
        self.scale (scale, scale)
        self.zoomLevel= zoomLevel

if __name__=='__main__':
    # this code is enough for loading an image and show it!
    app= QApplication (sys.argv)
    win= QMainWindow ()

    pixmap= QPixmap (sys.argv[1])
    qgpi= QGraphicsPixmapItem (pixmap)
    scene= QGraphicsScene ()
    scene.addItem (qgpi)

    view= OMITGraphicsView (pixmap, scene, win)
    view.setDragMode (QGraphicsView.ScrollHandDrag)
    view.show()

    app.exec_ ()
    # up to here!

# end

Things to note:

The code for loading, showing the image and pan support is only 13 lines of Python code, including 3 imports. The resulting app is also able to handle vector graphics, but of course I didn't exploit that, I just added a QPixmap/QGraphicsPixmapItem pair.
Zooming is implemented via QGraphicsView.scale(), which is accumulative (scaling twice to 0.5 actually scales to 0.25 of the original size), so I have to keep the zoom level all the time. There should be a zoom() interface!
The code for calculating the scale level is not very good: scaling between 75% and 50% or 25% produces scales of 0.666 and 0.333, which I think at the end of the day will accumulate a lot of error.
For the same reason, zoomToFit() has to do some magic. I also got hit by the integer division of Python (I was getting zoom factors of 0) so I had to add 1.0* to the claculations. It's good that this is fixed in Python2.6/3.0.
The size reported by the QMainWindow was any vegetable (it said 640x480 when it actually was 960x600), so I used the QGraphicsView instead. WTF?
For some strange reason zoomToFit() scales the image a little bigger than it should, so a scrollbar appears in the direction of the constraining dimension.
Less that 100 lines! Even if setupActions() could surely be improved.
In Marcelo's favor I should mention that he writes docstrings for most of his methods both in english and spanish (yes, of course I read his code after I finished mine). I barely put a couple of comments, but doing the same should add 10 more lines, tops. Also, I don't want to convert this into a who-has-it-smaller contest (the code, I mean :).
It took me approx 3 hours, with no previous knowledge of how to do it and no internet connection, so no asking around. I just used the «Qt Reference Documentation», going to the «Gropued Classes» page and to the «Graphics View Classes» from there.
It doesn't zoom with the mouse wheel either.
The default colors of ikiwiki's format plugin are at most sucky, but better than nothing.

Unluckly he didn't declared which license it has, so I'm not sure if I really can do this. I GPL'ed mine. ↩

.:: Marcos Dione/StyXman's glob ::. (Posts about omit)

Our man in Marseille

Our man in Toulon