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Wikipedia:Basic bitmap image editing

Ok you have this image. You think it would look great on a wikipedia page but it's not quite perfect. Perhaps it's too dark, or too big. If only you could clean it up a bit it would look great. Have no fear. This tutorial will show you a few tricks to turn an ok image into a thing of beauty.

Table of contents

1 Getting Started

1.1 The Image is too Big

1.1.1 Resizing
1.1.2 Cropping

1.2 The Image is Dark or the Colour is wrong

2 There is a tree growing out of someone's head

2.1 Using The clone tool to erase Offending Objects
2.2 See Also

Getting Started

The first thing to do is open up an image-editing program. There are several possibilities.

Adobe Photoshop The best in the business, it has lots of plug ins, is used by professionals, but is very expensive.
The Gimp Rapidly becoming very popular, and available for both Linux and Windows. For designing web graphics, GIMP is quite comparable to Photoshop, with the added benefit that it is free.
Paint Shop Pro Used to be shareware but now is sold reasonably cheaply (compared to Photoshop). Runs on windows machines.
CodedColor Provides less image editing functionality then Photoshop but included many useful tools like image viewing, creation of web albums, organization of pictures with keywords and annotations.
Adobe Elements[?] comes as part of some scanner and digital camera software. Described as for the serious hobbyist, it is a smarter version of Photoshop.
Microsoft paint[?] I have to mention it I suppose since it comes with the windows operating system. If you have a windows machine you don't even have to bother installing it. However, it is severely limited in what it can do.

For the rest of this tutorial. I will be describing how to use Paint Shop Pro to perform some simple image manipulations. {Only because this is the program with which I am most familiar, perhaps others could add sections on how to do things in the Gimp etc.} Here is a screenshot of PSP4 toolbar. I'm not going to go through what each button does, just the most important things.

The Image is too Big

Sometimes an image is so large it dominates the page. As a general rule, images should not be more than about 300 pixels wide. The image that you see on the right would be over 500 pixels wide if it were simply to be uploaded. There are several things that can be done about a very large image. If it is a scanned image, it can be rescanned at a lower resolution. If however the image is digital it must be either resized or cropped.

Resizing

Fig. 1 The Selection Tool in Action

Fig.2 Adjusting the Brightness

Fig.3 Removing the Tree With the Clone Brush

Select Image then Resize. You then get to choose the size of the image you want. Take care when resizing. The only way to make an image smaller is to throw away some of the pixels. If the image contains text, the pixels that get thrown away are not necessarily the ones that a human being would choose. If the top right pixel of the letter f is lost it becomes an t. Sometimes the only way to render readable, resized, text is to use the magnifying glass to look really close up, then pick up the correct colour with the dropper (the button that looks like a pipette), and finally select a one pixel paint brush to paint the letters in a pixel at a time.(The size of the paint brush can be adjusted from the style bar, which can be found on the view menu).

Cropping

If only part of the image is needed, it can be easily cropped. Use the selection tool to select the area that is wanted(see Fig.1) then copy and paste as a new image.

The Image is Dark or the Colour is wrong

If the image looks to bright or too dark it can be adjusted by clicking on colour then adjust then selecting brightness/contrast. A box pops up (fig. 2) with a small window that allows you to see the effect that any changes will have. Colour can be adjusted similaly by selecting red/green/blue instead of brightness/contrast.

There is a tree growing out of someone's head

Well not literally perhaps, but often there are parts of the image that you would prefer are not there. The trouble is if you simple delete them with the eraser tool, you'll end up with a great big splodge of the background colour. What you would like to do is remove the offending tree but leave the sky alone.

Using The clone tool to erase Offending Objects

The clone tool (the button with two brushes)copies one area of the picture to another. To use it, you first right click the area you want to copy from, then left click and drag the area you want to copy to. A black cross appears on the picture to show you where you are copying from. On the picture on the right, you can see the tree is being erased by copying a portion of the sky over the tree.