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Retouching Antialiased Text...


Retouching Antialiased Text

Antialiasing is used to smooth the curves and angles of bitmapped images, and is often employed to improve the appearance of text graphics. It achieves its effect by blending the edges of the foreground image with its background by adding pixels of intermediate colour. Read the section on antialiasing to find out how this works.

Sometimes antialiasing doesn't produce the best results right away. Take a look at the two images below...

The image on the left is as it was created, antialiased text with nice smooth curves and diagonals. But look closely and you'll see that parts of the image appear slightly blurred, particularly the vertical white bars down the centre of the 'g' and the second 'o', and the letter 'L'. The image on the right has been "retouched" and looks cleaner.

This enlargement of the first image illustrates the problem...

The program knows what to do with curves and angles, but can't make up its mind about horizontal and vertical edges. The first 'o' has been left with a clear gap down the middle, but bands of grey pixels have been added to the second one. The same has happened to the 'g' and the outer edges of the 'L'.

The result of antialiasing an image can be unpredictable, and sometimes these undesirable effects appear. But there's a simple answer. Touch-up the image manually and remove the unwanted colours.

In this step-by-step tutorial the screenshots and instructions apply to Paint Shop Pro but you can easily adapt the steps to most good graphics programs.

Step 1: Identify the Problem

Having created your image, take a close look at it. Use the Zoom tool to enlarge the image. Click the Zoom tool button on the toolbar. This changes the mouse pointer to the Zoom cursor.

Zoom tool
Zoom cursor

In zoom mode the cursor can be used to magnify or reduce the viewed size of the image (the actual image size doesn't change - you are just temporarily seeing it at a different size). Click the left mouse button to Zoom In (enlarge the view - up to 32:1). Click the right mouse button to Zoom Out (reduce the view - down to 1:24).

First, take a look at the image at normal size (1:1). This is the size at which you will be using it. Does it look OK? If it looks fine, leave it alone!

If it doesn't, then take a closer look. Zoom in to those areas that look a bit blurred. You're looking for extra coloured pixels that aren't needed. They will probably be against the horizontal and vertical edges of the letters.

Zoom in to at least 5:1. I often work at 10:1 magnification to do this job.

You might find it helpful to switch on the grid. Choose View > Grid to turn it on. To start with you'll see the default grid. This shows the image at 10:1 zoom with the grid set at 10 x 10 pixels...

The scale of the grid displayed depends upon the zoom level. It is possible to display a single-pixel grid when working at high magnification. To change the grid settings choose File > Preferences > General Program Preferences... and select Rulers and Units. Set Units to Pixels and both Horizontal Spacing and Vertical Spacing to 1. Click OK to apply the settings...

Now you can see the individual pixels that make up your image. It's time to start making improvements...

Step 2: Prepare the Tools

Your task is to remove any unwanted pixels by painting them out. Of course, you're not actually "removing" them but changing their colour so that they match the background. You can work with the grid on or off - it's up to you. In the illustrations that follow I've switched off for clarity.

First you have to charge the brush with the appropriate colour. You can do this using the Colour Palette but I prefer this quick method...

Click the Dropper Tool button to change the cursor to the Dropper Cursor.

Dropper tool  
Dropper cursor

Point to a part of the image showing the background colour (in this case - white) and click the left mouse button. This action charges the brush with the colour of the pixel you clicked on. (In fact you have now set the palette's foreground colour.)

Now click the Paint Brush button to change the cursor to a Paint Brush.

Paint Brush tool
Tool options

Click the Tool Options button to open the Tool Options window and set the Size to 1 and Density to 100. The other settings don't matter here. This creates a brush tip of 1 pixel in size, letting you paint a pixel at a time.


Step 3: Paint the Pixels

Each time you click on a pixel (remember to left-click, you picked up the colour left mouse button) you fill a pixel with the chosen colour. In other words, you make it disappear!

You can paint out one pixel at a time or, by dragging with the left mouse button, paint over a line of pixels. This takes a little practice - the Undo button can be very useful here!

Paint out a few pixels at a time and zoom out to 1:1 frequently to check the progress of your work. Remember, the object is not to remove all the grey pixels, just the ones that degrade the image.

When you are satisfied with the result. close and save the image. Job done!

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