Preparing Pictures


Photographers will be very familiar with the process of preparing photographs for display and will already have their own favourite software with which they are familiar. Many artists, on the other hand, are less familiar with preparing photographs of their artwork for display on a web site. This section provides a basic guide to photographing artwork and then processing the photograph using a free image manipulation program called GIMP.


It is of course best to start with a good photograph of the subject before trying to use computer software to compensate for a poor picture. The following guidelines are based on my experience of photographing artwork. I am not a photographer and just use a typical digital camera, nothing special, so this is targeted at artists. Apologies to any photographers that may read it.

Lighting. Even lighting of the subject is important. It is difficult to achieve this indoors without specialist equipment so the best option is to photograph outdoors but avoiding bright sun. If you have no option but to photograph indoors then choose a spot with good daylight but no direct sun. You may find that a piece of white card used as a reflector can help even out the lighting. An acrylic board is ideal. However you set up, make sure the flash is off!

Set up. The subject should be placed on an easel as near to vertical as you can achieve. It goes without saying that your subject must not be behind glass! Your camera should be on a tripod not handheld. Adjust the height and angle of the camera so that the subject is square in the viewfinder. Because the subject will probably be tipped back a little, the camera will need to be slightly above the subject and tipped forward to compensate and avoid the keystone effect. Try to avoid using zoom on the camera and leave some of the background around the subject. This can be trimmed off later in the processing.

Taking the shot. Your camera should be on a tripod so it should be possible to gently press the shutter release until it focuses and then gently take the shot. I good tip I picked up is that if your camera has a short timer then use that to avoid any possibility of camera shake.


Now we have taken our best possible photograph we will process it using GIMP. To better illustrate the process I will be using a poor photograph of a subject with all the mistakes I have told you to avoid above. However, even if you have taken the best photograph possible, some of the steps below will still be needed to get the best result. The photograph I will be using is this:

If you want to follow the processing steps then you can download a copy of the original here. To download the file, right click the link and select ‘Save Link as …’.

The first step is to get GIMP. The GIMP website is Follow the download button and get and install the latest version for your operating system. The version of GIMP I am using is 2.8.14

When you first start up GIMP you will find it has 3 windows: the left hand window headed ‘Toolbox’, a right hand window headed ‘Layers – Brushes’ and a blank central window  headed ‘GNU Image Manipulation Program’ with a menu bar. Although it is possible to use GIMP in this default layout it can be a bit confusing for a less experienced user as it is quite easy to lose the side windows. It may be easier to use a more familiar single window  layout. Under the Windows menu option select ‘Single-Window Mode’. This is the layout I will be using below.

Start by opening your image file using File/Open….

Rotate the image

The first thing I need to do with my picture is to rotate it. Use Image/Transform/Rotate 90% clockwise.

Rough Crop

To make further processing easier, make an initial rough crop to remove extraneous surround. Choose the Crop Tool, as shown below, from the toolbar, Roughly draw out a rectangle by clicking near the top left of the picture and dragging to the bottom right. There is no need to be accurate as the rectangle can be easily adjusted by clicking on any side of the rectangle and dragging as required until you have something like below.

Then either double click the image or press the Enter key to give:


Now comes a magical tool that I have found only in GIMP. It can deal with a keystone effect and with slight slopes on the image. The tool is the Perspective Tool and looks like this:

What we are going to do using this tool is to click and drag each of the three corners in the order shown below as indicated by the arrows.

When you click on the first corner a dialogue box will pop up and a grid will appear over the picture. The dialogue box is probably covering part of the picture so move it out of the way somewhere before starting to drag. Click back on the corner and drag to the left as shown. You are trying to get the left hand side of the picture vertical. When you are happy with it go on to corner 2. This wants dragging up and to the right as shown and you are trying to get both the right hand side of the picture vertical and the top horizontal. Finally drag corner 3 down vertically to make the bottom of the picture level whilst retaining the vertical side on the right. If you make a mess of it and want to start again, just find your dialogue box and click the Reset button. You should finish up with something like this:

When you have got this, click the Transform button.

Final Crop

Finish off the trimming of the picture using the Crop tool as described above. You should now have:

Adjust Levels

The final adjustment is to the appearance of the picture. This is done using the ‘Levels’ tool which is found using Colours/Levels… When you select this you are presented with a dialogue showing a graph that looks like this:

The graph shows the distribution of colours throughout the image from blacks on the left to whites on the right. An ideal graph would have values throughout the range but most, like the above, have no values at either the blacks end or the whites end or both. The dialogue is used to adjust the levels. Initially try just clicking the Auto button near the eye droppers towards the bottom of the dialogue. If you are happy with the results then just press OK. Alternatively you can try adjusting manually. Click on the black half triangle under the graph and drag it to the right to just before where the slope of the graph starts to rise. Do the same from the white end. It should look like this:

You can see the effect of the changes on the picture as you are moving the sliders. Sometimes having them right up to the curve may give too extreme an adjustment and you may get better results with the sliders back a little. Play around until you are happy and then press OK.

You now have the finished result which should look like this:


To save the finished picture you do not use any of the various Save options in the File menu as you might expect. These are used to save an image in GIMP’s own XCF format and we require jpg format. To save in jpg format use File/Export… By default it will offer to save the file with the original filename and directory. If you do not wish to overwrite the original, change either the filename or directory.


Finally, close the image using File/Close. This will ask if you want to save the changes but also say that the file has been Exported. This is asking if you want to save your changes in native GIMP format which you don’t so choose Close without Saving.


On first sight the above steps may seem very daunting but they consist of the following steps which soon become familiar:

  • Open
  • Rotate if required
  • Initial crop
  • Adjust perspective if required
  • Crop
  • Adjust levels
  • Export