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.