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Hello,

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

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

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

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

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

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

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

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

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

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

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

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

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and boldly push contrats to the maximum.

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

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

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

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

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

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

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

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

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similar process. Done, in a record time.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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Here is what I’m going to work with.

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

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

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

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to place the head wherever I want. In fact,

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

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

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

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

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it almost systematically with portraits.
Here is how.

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

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called “Fuzzy Border”. When the option windows appear

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

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image” option, which generates a single-layer

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

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this option.
The second thing is the border size.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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I do the same with the other mask.

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

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

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

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

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

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

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clones, which will give it a bit more consistency.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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to the lithography.

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

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

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

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

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

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

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

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

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

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stamp, with colors that harmonize better with it.

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

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

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

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

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presentations where software tools
appear, but not only as you

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are going to see.

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

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

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images, including many shots of my own screen.

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

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

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

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

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... or something else.

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

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

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

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

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

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focus on ONE precise point. No distraction.

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If using screenshots is natural in 
a presentation linked to programming

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

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

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difference between two sets.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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transitions, of course.