Pythonneries - Making Of 7

Hello,

I have explained how to manage with
Gimp, I’m now going to give a

number of practical examples. I said it
at the beginning of this series, whenever I talk

about someone, I like to show that someone
and, to use the example in the previous

video, I find it hard to talk about
the “Pascaline” without showing Blaise Pascal.

The mock Internet search of my video on
shapes, and I get a lot of portraits

Pascal. Let’s say that we choose this lithography.

As is, it wouldn’t look too good and
I must remove the background, but

I can do this very quickly and very easily
with Gimp, using almost only options from the

“Colors” menu. First thing, let’s get
rid of this pink beige color

old paper background. In the
“Colors” menu, “Desaturate” will

turn everything to shades of greys. But
I don’t want grey. In the same menu,

I’m going to switch to “Brightness-Contrast”,

and boldly push contrats to the maximum.

switching “Color to Alpha”. The Alpha channel,
if you remember the previous video, is

associated with transparency – and even
if you have forgotten to state that your image

knows transparency, this option will enable
it automatically. By default, the color to

make transparent is white, which is
what we want. Click OK, and we get

a good lithography that we can use
with anything. Perhaps that we’ll remove

the legend an the name of the long-dead,
artist, which we can achieve by

selecting with the lasso and cutting.
Then, why not, we can add Pascal’s

own signature, found on the web
and that went through a very

similar process. Done, in a record time.

At this point, we can stop and think.
I have no clue about where this Pascal

portrait is coming from, but my
guess is that this lithography dates back

to the 1830s/1840s, and smacks of romanticism.
It doesn’t look like an authentic portrait.

In fact, this poor Pascal rather looks like
a teen-age idol in this lithography. Is that

the way I want him to look?
Not so sure.

Let’s happily go from one extreme to the other.
I’ve found this stamp, still on Internet.

Technically speaking, it’s an engraving,
but here it rather looks like

Dr Frankenstein’s failed first attempt.
Aside from style, let’s check how we

can make this portrait usable, because
techniques that were previously used

won’t give a good result here.
The image is a .jpg file, I’m therefore

first going to add transparency, the famous
“Alpha channel”. Next, I don’t want

this portrait to look like a stamp.
I’m going to use the selection tool in

the toolbox, and draw a rectangle
around the area of the image that I want

to keep. In the “Image” menu I’m going
to choose “Crop to Selection”,

Here is what I’m going to work with.

First of all, I’m going to remove the background
around the head, using the lasso a little,

and the eraser much. I’m getting an image
that wouldn’t be that bad, except for

something very ugly, those awful straight
lines. What is the issue? I won’t be able

to place the head wherever I want. In fact,

even if I put it in a corner, I’ll always have
a straight line to remind that it’s a plain

cropped stamp. Contrast this with
the previous lithography, with its

curves and lower dim area, which
allows any type of lay-out. In fact,

We can get a similar effect with Gimp
for any type of image and I do

it almost systematically with portraits.
Here is how.

We’ll use a filter, the one under “Decor”

called “Fuzzy Border”. When the option windows appear

Two things need to be changed.
The first one is the “flatten

image” option, which generates a single-layer

image. I want to update the layers after
the filter has run,and I must uncheck

this option.
The second thing is the border size.

Out of experience, what works best is
a border the size of which is around

about 1/7th or 1/8th of the smallest
image dimension – obviously, it doesn’t

need to be precise down to the pixel,
I always wildly round numbers. Here,

my image is about 300 by 400, and I’ll
use a value of 40 for the border. I apply

the filter, and I get a two-layered copy
of the image, with a top layer (that

happens to be the active one) being a
kind of fuzzy white frame. I want to

see some things fuzzy, mostly the chest,
but not everything and not the head. So I’m

going to use the lasso to select the part
of the mask that I want to remove, over the

shoulders.You’ll notice that the lasso
allow you to move outside the image and

circle around it from a distance. This
area, I remove it. At this point, you shouldn’t

forget to go the the selection
menu and choose “All”.

If you don’t, you may have surprises in
the next steps.

OK, now we have two layers, the
top layer which is the active one

(here indicated by a red frame) and
contains a blurred mask, and the bottom

layer, the portrait proper. I go
to the 'Layer' menu and choose

to duplicate the current layer. Using
the layers window I’m going to select

the bottom layer, and duplicate it
as well. Now, it’s getting complicated.

I select any of the two blurred masks and
in the “Colors” menu I select “Invert”.

It becomes black. And now beware, the
order needs to be precise: using arrows

in the layers window, I’m going to place,
from top to bottom, the white mask, one Pascal,

the black mask, and the second Pascal. I
make one of the two masks, here the black one,

the active layer and click on
“Merge down” in the “Layer” menu.

I do the same with the other mask.

Now, let’s deal with transparency: we
we select the top layer, then, in the

Colors menu, we are going to click on what
we have already seen, “Color to Alpha”,

and make white transparent. then we select
the other layer but we’ll change the color

to make transparent by clicking the color
and switching from white to black.

This time, black will disappear and I’m
going to end-up with a rather ghostly layer.

So ghostly in fact that usually I’ll
duplicate it and then merge the two

clones, which will give it a bit more consistency.

And here we are, we have fuzzy image border.
If you need to put this image on a dark

background, I’ll advise you to add a black
layer at the very bottom, and inspect

closely. Very often you notice in the
light layer that previous erasures

were so so, and sometimes you have
a slight halo that doesn’t look too good.

All this is easy to fix with the eraser.
When everything is OK, you can remove

the black layer, and merge the two remaining
layers. There is one remaining problem that

doesn’t show too much here but is very noticeable
on a color image: I have removed white and I have

removed black, so globally I have removed
grey. Removing grey from colors, that’s

the opposite of making them greyer, and
therefore I have saturated colors. I can

swear you that with a color picture
the soberest individual will look

like a second Falstaff. This is why
I usually end up with the “Colors” menu

and roughly desaturate colors, trying to
match colors in the original picture.

I end up with an image that is far easier to use.
In this particular case,

I still have a small straight line. It’s no
big deal, I just have to line up this side

with the edge. And finally, aesthetic choices
apart, the stamp ends up being quite equivalent

to the lithography.

With all this, how do I introduce Pascal’s
computing machine? Not like this,

as you may guess. Here is what I have
shown for real during a lecture to my

American students. First of all, drum roll:
a date, which corresponds to nothing

known because as anybody knows between
1492 and 1776 not much happened.

This is puzzling. With the date, I associate
an exotic location – I have found, still

on the web, a map of Rouen (modern spelling) in 1655,
a few years later. I guess that at this time

cities were evolving slowly. The plot
thickens. Then another Pascal portrait

that I initially prepared as a background
for quotes. And finally over this

the computing machine. Needless to say,
I could now use as well the transformed

stamp, with colors that harmonize better with it.

There is a light topic I want to talk of,
screenshots. There are tons of ways to

get a screenshot, you can very easily
do it with Gimp, under the

File/Create/Screenshot menu. You
can take a fullscreen image,

or only a window or an arbitrary area,
and it’s very useful, first for

presentations where software tools
appear, but not only as you

are going to see.

I like to eat my own dog food, and as
in the videos about shapes I mostly

used shapes, in this and the
previous ones I have amply used

images, including many shots of my own screen.

If there is something I don’t like
in a video recording of one’s own

screen, it’s how indiscreet it can be.
You needn’t know whether I’m running on

Windows, Linux or Mac. It’s none
of your business. And wallpapers!

I don’t want to let you know whether
the gentleman that I am prefers blondes

... or something else.

One confidence: Jack Lemmon isn’t my type of girl;
but I like movies.
I don’t want you either to know if

my legendary repute for modesty is well
grounded, or whether I am actually hiding

slightly megalomaniac tendencies.
Solution? Take a screenshot of THE window

of interest, and show nothing but this window.
Even better, only show from the window

the part I am talking about, and I can even
play with blurring and desaturation to

focus on ONE precise point. No distraction.

If using screenshots is natural in
a presentation linked to programming

or IT topic, you can use them in a
far subtler way. Imagine that I

want to talk about set operations,
and show intersection, union and

difference between two sets.

I can use two circular shapes in different
colors to represent my sets.

The snag, it’s that when I put them together
I cannot show easily intersection,

union and difference. All right, for union
I might change colors and give the same

color to both shapes; but the single
black circular arc in the middle ruins

symmetry. For intersection, I can make
colors transparent, and intersection

appears different, but this doesn’t leave
many options when choosing colors.

To show the difference, it’s kind of hopeless.

What shall I do? These shapes are in my
Powerpoint window. I’m going to zoom

over them as much as possible (I set the slide
view option at 200%) and take a screenshot.

I’m going to remove the background of this image
and color three different versions. As an

aside, I won’t elaborate on it, but to
color an image is far less easy than it

looks, I often use two layers, only
keeping black lines in the top

one and splashing colors in the bottom layer.
And know, what shall I do? First

slide, my shapes, which are separately animated.
Next slide, fade over an image that I have

sized to exactly match the size of the
shapes and that I have put on screen

exactly at the same place as the shapes
in the previous slide. It’s like a

stuntman replacing the star. Another image,
another image, and back with shapes.

I have have shown what I wanted, nobody
saw substitutions nor technical switches,

the message got through. And what shall
we talk about next? Animations and

transitions, of course.