changing background

Open the skull and hat png file from the previous post with gimp. You should have something like this;

The gray and black checkerboard is transparent and the white is simply white. As is now, if we added a background layer it would only show through where the checkerboard is, which is not what we want. We want the background for the whole background, including in the nose and eye sockets.

To make the white background transparent;
     [Tools | Selection Tools | By Color Select]
Click once on the white background to select all the white and then right click and from the pull down menu select;
     [Edit | Clear]
The entire background becomes transparent, and is represented as a grey checkerboard. This is a useful file to have, so you may want to save a copy and export a copy as a png file. {see previous post for howto}.

Now, we are going to do two different types of backgrounds. We are going to create one, and use a different graphic for another. Before we start, you may have noticed there is a crawling dotted line around the hat, skull and whole graphic. This is because the 'select by color; white' area is still selected. We need to un-select  everything with;
     [ Select | None ]

1) Creating a psychedelic background
     [ Layer |New Layer]
You can name the layer anything, but we will call it clouds. Set the fill to white. Your graphic should now be a big white square. The layer should be the active layer, but just to be sure, click on it in the layer toolbox.
Now do;
     [ Filters | Render | Clouds | Plasma ]
 and accept the defaults. Then do;
     [ Layer | Stack | Reverse order ]
You now have a skull with hat on a nifty psychedelic background.
 It should look like this;

Pretty cool, huh?

2) Using another graphic as background
I found this really cool graphic of a pirate ship I want to use as background. Its actually the pirates bay ship.

Copy and save the jpeg then drag a drop into your already open gimp. It will show up as another layer. If you are lucky it should insert behind your hat and skull layer but before your cloud layer. If not, in the layering toolbox you can click and drag a layer up or down. Adjust the layers so it is skullnhat, pirateship, and then clouds. It should look like this;

I'm not sure I like it, but lets continue.
Now, the ship layer is much bigger than our graphic, [the dotted line is its borders]. We can export it now and get a .png the size of our original skull and hat, or do;
     [ Image | Fit Canvas to Layers]
This is the result;

I don't really like the result, I should have found some clouds, but that is how to use a different graphic as background.
Here is the result of essentially the same process, but with clouds as background.

Hmmm. I guess they are both ok.

merging images

Here are two simple images I wish to merge.
A skull & crossbones with a purple headscarf ;

and a hat;

The goal is to put the hat on the skull and have everything look natural.

Start Gimp. Open the hat picture by dragging and dropping it into Gimp.The hat picture is slightly bigger than the skull and crossbones, so we open it first.

Next, add an alpha channel.

     [Layer | Transparency | add alpha channel]

Next, add the skull and crossbones by dragging and dropping it into Gimp. It will add it as another layer. It will look like this;

Now, reverse the layer order and make the hat the active layer.

     [Layer | Stack | Reverse layer order]

or

     [Layer | Stack | Layer to bottom]

The result is the hat will be on top, blocking out the skull. The skull however, is still the active layer and we want the hat to be the active layer. Make the hat layer active.

     [Layer | Stack | Select top layer ]

We now want to make the white background of the hat transparent. To do this we select the white area and erase it. We an select the area by color or by fuzzy select.

     [Tools | Selection tools | By Color select ]

or

     [Tools | Selection tools | Fuzzy Select ]

Right click in the white area and from the drop down menu select;

     [Edit | Clear]

The result will look like this;

Now, use the move tool to move the hat layer up so the hat fits on the skull. 

The grey checkerboard is part of the transparent part of the hat layer. The white is the non transparent part of the skull layer.

Next, we will merge the layers and export our new graphic as a png.

Merge layers;

     [Layer | Merge Down]

Export png.

     [File | Export]

In the box that comes up, in the Name field give your new image a name. Ending it with .png will export it as a png file. [if you end the file with .gif, .jpg, .bmp it will export it as that type of file.]  In the png popup, accept the defaults and export. When you close gimp it will tell you that your file hasn't been saved. Gimps own default format  is .xcf. You can save a .xcf version if you plan on doing further work with the file, but otherwise its not needed. That is it!

Here is the result;

Introduction

GIMP is a free Image Manipulation Program. It can be used for image retouching and editing, free-form drawing, re sizing, cropping, photo-montages, converting between different image formats, and other more specialized tasks. It works on Linux, OS X, and Windows.

I am no expert with Gimp, but have used it on and off for the last couple of years.

You can do some pretty amazing things with Gimp, but for someone who doesn't edit pictures on a regular basis, some of the procedures appear convoluted, cryptic, with precise steps not easily remembered. I'm sharing this blog with the world, but it is really  more for me, grouping all these procedures in on place.