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Graphics editor GIMP and office suite LibreOffice explained
With summer just around the corner, there’s every chance you’ll have hundreds of photos on your Mac that need editing and tweaking at some point. But if iPhoto isn’t up to the daunting job, give the ‘GNU Image Manipulation Program’ (or GIMP, for short) a try.
This free-to-download image-editing software has many of the high-end features you would expect to find in pro-level apps such as Photoshop. These include tools and elements such as paths, lassos, alpha channels and layers. However, unlike the Adobe apps, which cost a pretty penny, GIMP is totally free to download from gimp.org. Plus, because it’s an open-source program, GIMP is constantly being updated with new features and plug-ins to help it keep pace with its high-end competitors – all free of charge!
The working environment in GIMP will be familiar to anyone who has used an image editor. There’s a collection of tools on the left-hand side, and palettes (known as ‘dialogs’ in GIMP) on the right, featuring layers, gradients and your
This free image editor has many of the high-end features found in pro apps such as Photoshop
document history. You can find out more in our annotated image at the top of the page opposite.
When starting up GIMP for the first time, you’re given the option to choose one of two screen modes – multiwindow or single window. Multi-window is the default and enables the dialogs to be moved around at will – ideal for users with more than one screen. Single window mode creates a rigid interface, with dialogs in fixed positions, which is similar to iPhoto or Photoshop Elements – perfect for beginners.
On the surface, GIMP may seem familiar, but there are some significant differences, so whether this is your first time with GIMP or if you just want a quick guide to some of the features,
we’re going to run through five common image-editing techniques and how to achieve them.
Cropping your images
Select the Crop tool from the Tools palette (it looks like a scalpel), and create your chosen crop by dragging and selecting. If you don’t get it right first time, don’t worry, you can tweak the selection area using the highlighted square areas in the corners.
To keep the aspect ratio constant (the relationship between the height and the width of the image), hold down ß when making your selection, or select the Retain Aspect Ratio checkbox in the Tool Options palette on the lefthand side. In here, you can also amend other variables, such as the output size of the image you are creating, as well as the resolution.
To straighten an image, just select theRotate Layer tool from the Tool palette, which brings up a grid to help you line up your picture perfectly, or you can enter rotation values as numbers to get your horizon perfect.
If you think iPhoto’s ‘Enhance’ function is a bit limited, GIMP has a number of powerful colour-editing tools, which can be found in the Colors menu. The most basic option is Brightness and Contrast, which enables you to make quick and easy tweaks to the lightness and darkness of your image. But if that’s still too basic, try Hue and Saturation. This allows you to edit the colours in your image with more accuracy, as well as adjusting the brightness of some or all of the colours in to remove colour casts or fix similar issues. You can also do
this using Colour Balance, which lets you adjust colours in the highlights, shadows or mid-tones respectively.
These three are still relatively basic, so if you’re feeling more adventurous there are also Levels and Curves. These will be familiar if you have any experience using higher-end imageediting programs, such as Photoshop. They let you adjust the tonal range of the image through the image’s histogram (a visual representation of the colours within your image). You can manipulate points on the curve or the points underneath the Levels histogram to get the perfect image.
If you’re not comfortable making these kinds of manual changes, there are ‘Auto’ options for all these tools, which perform fixes to your images at the click of a button.
If you’re looking to apply a colour change to a specific part of the image rather than the whole thing, GIMP has a fantastic collection of selection tools. As well as the standard rectangular and elliptical Marquee tools, there’s also a freehand Lasso tool, which enables you to select parts of your images by drawing around them with your cursor. With any selection tool, once you’ve made your selection, a dotted line appears on the screen (known colloquially as ‘marching ants’), and you can then apply adjustments to just these parts of the image.
If you’re after some more sophisticated options, you can use the Intelligent Scissors tool, which allows you to select areas of your image using a smart lasso. Simply draw points around the subject you want to tweak and GIMP attempts to detect its edges, filling in any gaps. If it doesn’t appear to have found the edge correctly, you can add more points or move existing points around until they are just right. Once drawn, simply click in the middle of the selection and the ‘marching ants’ appears, turning it into a selection.
Working with layers
Here’s the key thing that iPhoto does not offer. As image editing gets more complex, it‘s worth beginning to work with layers. Layers allow you to stack up parts of an image on top of each other and move them around without
affecting the area beneath – it’s as if your image is a stack of papers and you can move the sheets around independently of each other.
To work with layers in a nondestructive manner, use Layer Masks. See our walkthrough starting below on the oppposite page for a quick guide.
Resizing and saving
Once you’ve finished editing your images, it’s time to decide how you want to save them. GIMP supports all major image files formats, including JPEG, PNG and TIFF, as well as it’s own native format, XCF. Be aware, though, that GIMP only saves your editable, working documents in XCF mode, so to produce a JPEG version of your image, you have to use the Export command, rather than Save As.
To resize images for web use or to make low-res thumbnails, go to Image > Scale Image. Here you can see the image’s dimensions and edit them accordingly. By default, they appear measured in pixels (px), but this can be changed using the drop-down menu if you prefer. Here you can alter the size of the image in order to reduce it for posting online. Any changes you make to the pixel dimensions alters the physical size of the image and so reduce the overall size of the file, which makes it perfect for uploading. Just remember to make sure the image is set at 72ppi, which is the standard for digital images on the web.
For print images, go to Image > Print Size and here you can adjust your image for printing out. If you alter the width and size, remember to retain the pixel dimensions, to ensure you get the highest image quality you can for printing out.
Once finished, you can save your image in a variety of formats. For online images, choose JPEGs and apply compression to reduce the file size even further – but be careful with applying it heavily, or the image becomes blocky and ‘artefacted’. For files with individual layers you wish to retain, save them as TIFFs – but be aware they’ll be very large file sizes.
Multi-window mode lets you position dialog boxes wherever you’d like them.
When rotating an image in GIMP, a grid will appear to help you to line up your verticals and horizontals.
Adjust your images’ colour balance simply and easily using Curves.
Edit the size of your images for web or print and export them as JPEGs, PNGs or TIFFs.