Re: [Gimp-user] Accessory List

[Steve Kinney <admin pilobilus net>]

On 10/15/2015 02:30 PM, Nick Longobardi wrote:
> Hello, I was reccommended to gimp my a fellow graphics worker and wanted to
> ask about some accessories. She said it's very close to Adobe Photoshop and
> I am mainly looking for the special magic eraiser that can erase within a
> predetermined shape, say making the inside of a square transparent but
> having the borders still

There's lots of ways to do that, but first:  Do be aware that the
GIMP is a "full featured" image editor; doing simple things with it
is easy, but not obvious unless you have used it before, or checked
the manual for instructions.

The GIMP is more or less interchangeable with Photoshop in terms of
end results, but their commands and "native workflow" are only
deceptively similar; they really are two different beasts.

To erase within a predetermined shape, is really the same thing as
filling a predetermined shape with one color:  The "erase" part is
one step, but drawing the shape for your hole will take more or less
effort considering how complex the shape is.  For instance, neatly
cutting out photos of people is a chore, while neatly cutting out
rectangles of any size is a breeze.

One of the /many/ ways to "make a square transparent" while leaving
the picture around it alone:

1)  Open your original image in the GIMP.

2)  You should see the image in one big window, and a way smaller
thumbnail of the image will show up in your Layers dialog box.  If
you see that thumbnail, click it with your right mouse button; if
not, use the menu above your image to select Layer > Transparency >
Add Alpha Channel - if Add Alpha Channel is grayed out, that means
your image already has an Alpha channel.

The Alpha channel is the part of an image file that stores
"transparency," so you need that Alpha channel for the job at hand,
"cutting a hole."  JPG files don't have it, PNG files do.

3)  Left click on the toolbox button for "rectangle select."  It
should be at the top left corner of the field of tool buttons.  It
has a rectangle on it.

4)  Right click inside your main image window (the "canvas"), hold
the button down and drag it across the image to select your
rectangle.  When you let go, you will see its outline.  Move your
mouse over this outline near the edges to get "handles" you can
click and drag to adjust your rectangle.  Do that until it's "just
right."

5)  On your keyboard, do Control+x to delete the selected area.  You
should see it replaced with a dark checkerboard pattern.  That's it,
your mission is accomplished.

6)  Save your work.  On your keyboard, do Control+s.  The Save Image
dialog box will open, just click the save button.  This gives you an
XCF file, that is, a GIMP file that allows you to pick up where you
left off if you need to make changes or additions to your work.

7)  Create a new image file.  On your keyboard, do Control+e.  The
Export Image dialog box will open.  Save your image as
"some-name.png"  The .png at the end tells the GIMP to save the
image in that format, which has an alpha channel and will preserve
your hole "as a hole" rather than filling it with a background color
(i.e. white).

But that png file sounds pretty useless to me, without something to
fill the hole you made.  So now let's go back a couple of steps:

5)  When you are satisfied with your selection, find the Foreground
and Background Colors selector, in the Toolbox below the buttons:  A
black rectangle over a white one would be typical.  Left click the
top one to open your color selector.  Click and drag in the big
rectangle and the tall skinny rainbow to get the color you want.

5)  When you've got the right color, click OK to close the color
selector.  With your mouse, drag and drop the top color in the color
selector into your image canvas.  Viola, your selection is filled
with that color.

Then proceed to save and export the image as above.

If you want to fill that rectangle or other shape with part of some
other image, that's not at all hard:  Add the image you want to
include to the open image file in by dragging and dropping it from
its file folder or your desktop into the image canvas.  You will put
it under the layer you cut a hole in and viola, it shows through.
But it's best to learn about layers in GIMP images here:

http://docs.gimp.org/en/gimp-layer-menu.html

:o)

Steve