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• Understanding Graphic & Image File Formats – Bitmaps versus Vectors
• Using Guides and the Guides Layer in CorelDraw
• Corel PhotoPaint – Create your own Impressionist Painting Effect

or click here to go to see this month's "Top Tip"

For most people, the main sources of bitmap images are the internet, digital cameras, scanners and "Paint" programmes such as Corel PhotoPaint, Adobe PhotoShop, and PaintShop Pro – to name but a few.

Generally speaking, bitmap images are referred to as being "Device Dependent". This means that their resolution – and thus the quality of their appearance – is tied to a specific output device whose properties were known at the time the image was created. This resolution can never be changed (except by using specialist software). One consequence of this is that the images can not be re-sized successfully. Although most Desktop Publishing, Graphics and Word-Processing software these days will allow you to re-size a bitmap, the quality of the resulting image will usually be poor, and it is this that gives rise to "the jaggies".

Common Bitmap
File Extensions/Types

In order to fit that number of pixels into 1 square inch, the pixels are carefully composed to a specific size: too big and they will not all fit; too small and they will not fill the area which would leave white spaces or areas where the colour is less dense. (This is exactly how shades of colour are created.)

Suppose you then placed this image into a document in a DTP or Word Processing programme, but decided that you wanted it to be bigger – say twice the size. When you re-size a bitmap like this, what you are actually doing is stretching the pixels that make up the image. What you should really do is to add pixels to the image to make it bigger, but very few DTP or Word Processing applications have that capability. (Look for a "Resample" command to find out if your programme can do this.) Remember that a doubling in size like this actually results in each pixel becoming 4 times larger, since you are doubling both the width and the height of each one.

The image on the right illustrates the jagged effect that is produced when bitmap images are re-sized without altering their resolution. Not only is the size of each pixel increased, but the size of the "steps" between them is also increased, and this is what produces "the jaggies".

Whilst the result may not look too bad when viewed on your computer display, the printed image will almost invariably be of very poor quality.

• Always create your images at the size you will need them to be in the finished work – never scan or create small to reduce file size and then re-size later
• Set the resolution according to the final output device that will be used to print or display the image. For example, an image to be used on a web site or in a PowerPoint presentation will look perfect at 96 dpi. The same image printed on a colour laser printer will require a resolution of at least 250 dpi. If you are sending work to a bureau for remote printing, ask the service bureau about the optimum image resolution for their equipment
• NEVER re-size bitmap images. If you need to make them bigger, re-scan to a larger size if possible, or resample them if your software has this capability

CorelDraw, Adobe Illustrator, Macromedia Freehand and AutoDesk's AutoCAD are all examples of software that create this type of vector file. Artwork created by these applications will have a "drawn" appearance rather than the "painted" or photographic quality usually associated with bitmaps. The "Clipart" libraries supplied with Corel, Microsoft, Adobe and other software are mostly made up of vector graphics.

However, vector graphics may include bitmaps, and a vector file can be converted to a bitmap – so don't rely purely on the appearance of a graphic to determine its type!

The disadvantage of vectors is that they are virtually useless for graphics and images that will be viewed on a computer monitor. This is because a monitor is itself a bitmap device and cannot display a vector graphic.

When you are working with vectors, then, What You See (on screen at any rate) is most certainly not What You Get when you print! Vector graphics programmes produce bitmap copies of the underlying vectors for on-screen display purposes (sometimes called a "header" or "preview" file). This is usually a low-resolution (to reduce file size and improve performance) bitmap copy of the underlying vector, which does not look very good on-screen, although  "bitmap smoothing" technology is improving all the time. When the file is printed, the software sends the vectors to the printer not the bitmap.

Common Vector File Types/Extensions

The graphic (right) used as a logo for the PPA "Win the Website Wars" course was created as a vector image in CorelDraw. This shows what we mean by the "drawn" appearance typical of this type of graphic. In all of the printed material relating to this course, the original vector graphic is used. However, because you are viewing this on a computer monitor, we've created a bitmap copy of it, which is what you are seeing here.

If the final output will be a display device such as a computer monitor or data projector, then you need to use bitmaps. Graphics intended for websites, or for PowerPoint presentations all use bitmap devices (a computer screen) as the final output device, and as these can not display vectors, there is little point using this format.

We hope you have found this brief overview interesting and useful, and that it will help to explain some of the "mysteries" surrounding different file formats.

PPA runs regular courses on graphics and desktop publishing software, and is an approved Corel Training Partner. Click here to see the CorelDraw Introductory course outline; here for the Advanced course outline; or here for the Corel Graphics Suite Introductory course outline that includes training on both CorelDraw and Corel Photo-Paint.

We also run courses for most popular office software, including Adobe PageMaker, FrameMaker, Illustrator, QuarkXPress, and Microsoft Office. For details of availability and prices please contact us. For a full list of courses click here.

If you have any comments regarding this or any other page of this website, or if you have suggestions for future features on this Hints & Tips page, please contact webmaster@ppatraining.co.uk

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If you know all about Ruler Guides, click here to go straight to the section on Non Linear Guides.

Ruler Guides are non-printing horizontal, vertical or angled lines that can be placed on a page either by dragging them from the rulers on screen, or by positioning them precisely from a dialogue window. Objects can snap to guidelines to aid perfect alignment (View Menu, Snap to Guidelines)

• Ensure that the rulers are visible (View Menu Rulers)
• Place the cursor in the vertical ruler (for a vertical guide) or the horizontal ruler (for a horizontal guide). The cursor shape will change to a white arrow when it is in the correct position
• Hold down the main mouse button and drag on to the page. You will see a dotted line moving with your cursor. Release the mouse button when the guide is in the correct position. The guide will now appear as a dotted red line
• Click the main mouse button away from the guide to de-select it. Its colour will change to blue
• For an angled guide, place a horizontal or vertical guide as above, then, while the guideline is still red, click on the guideline again. If the guideline is blue, click on it to select it and turn it red, then click it again
• Rotate handles will appear on either end of the guideline, with  a centre of rotation in the middle of the guideline. The centre of rotation can be dragged to a new position if required in the same way that you would for any other object
• Place the cursor over either of the Rotation handles, hold down the main mouse button and drag to angle the guideline

• Click the guideline to be moved – it will turn red
• Drag it to a new position

If you need to position a guideline more accurately, drag it from the ruler as above, and then double click it to produce the Guidelines Setup dialogue window. Key in the precise horizontal and vertical positions relative to the current ruler's zero point, and specify an angle for an angled guide.

• Drag it back to the ruler, or
• Click once on it to turn it red, and then press the Delete key on the keyboard, or
• Double click it to produce the Guidelines Setup dialogue window, and then click the Delete button to delete the selected guide, or the Clear button to delete all of the guides currently showing in the Guides list box

In a new piece of artwork based on the default Coreldrw.cdt template, the Object Manager will display an icon for each page of the artwork, and an icon for the Master Layer. The Master Layer will contain nested levels that can be viewed by clicking the + sign to the left of the Master Layer name. If a - sign is showing, the nested levels are already displaying.

The 4 default layers are Guides, Desktop, Layer 1, and Grid. The name of the currently active layer appears in red, with a red page icon to the side of it.

Click on the name of the Guides layer to make it active. It's name will turn red.

Anything that you now draw on the page will be placed on the Guides layer, and will be treated as a guide. Guide objects will not accept Fills or Outline Pen styles.

Because Guides are placed on the Master Layer, any objects placed there will appear on all pages of your artwork.

Guides are only non-printing, because that is a property of the Guides Layer. You can have your guides print by clicking the Printer icon alongside the Guides Layer in the Object Manager. If the printer icon is grey, the guides will not print, if it is coloured, then the guides will print. In the illustration to the right, only Layer 1 will print.

The Pencil icon indicates whether a layer is editable or not, and the Eye icon indicates whether a layer is visible or not. You can change any or all of the Properties for any of the layers. In the illustration to the right, the Grid layer may not be edited, is not visible and will not print.

The Object Manager Docker

Now drag one vertical and one horizontal guideline from each of the on-screen rulers, and position them so that they intersect near the dead-centre of the page. You can judge the dead-centre by eye for this exercise.

Make sure that Snap to Guidelines is enabled. (View Menu)

Click the Rectangle Tool in the Toolbox, hold down both the Shift and Control keys on the keyboard, place the cursor on the intersection of the two guidelines in the centre of the page, and drag in any direction to create a rectangle.
(The shift key causes the rectangle to centre on the position the cursor is placed, and the Control key constrains the rectangle to a perfect square.)

Use the width and height boxes on the Property Bar to set the rectangle to 100mm square.

Use the Transformations Docker, (Arrange Menu, Transformations...) to create a 50% duplicate of this rectangle. You should now have 2 perfect concentric squares in the middle of your page.

Click the Pencil icon alongside the Guides Layer in the Object Manager to prevent any further editing of the guides.

Now click on Layer 1 in the Object Manager to make this the active layer.

Choose the Rectangle Tool again, and, using the larger of the 2 rectangular guides as a template, draw another rectangle over the guide rectangle. Snap to guidelines should make it easy to keep the new rectangle to exactly the same dimensions as the guide rectangle.

Choose Arrange Menu, Convert to curves to make the new rectangle editable.

Now Choose the Shape Tool from the Toolbox and double click on the midpoint of each of the four sides of the rectangle where the guidelines cross them. This will add a node in each of these positions.

Still using the Shape tool, drag each of the newly added nodes along the vertical or horizontal guideline on which it is placed until it reaches the border of the smaller rectangular guide, (not the dead centre of the rectangle guides).

Fill the resulting shape with a colour or pattern of your choice, and you now have a perfect 4 pointed star.

The Transformation Docker

We hope you have found this brief lesson in CorelDraw interesting and useful, and that it will have inspired you to experiment with other features of the software.

PPA runs regular courses on most of the products in the Corel Graphics suite of applications, and is an approved Corel Training Partner. Click here to see the CorelDraw Introductory course outline; here for the Advanced course outline; or here for the Corel Graphics Suite Introductory course outline that includes training on both CorelDraw and Corel Photo-Paint.

We also run courses for most popular office software, including Adobe PageMaker, FrameMaker, PhotoShop, Illustrator, Acrobat, QuarkXPress, and Microsoft Office. For details of availability and prices please contact us.

If you have any comments regarding this or any other page of this website, or if you have suggestions for future features on this Hints & Tips page, please contact webmaster@ppatraining.co.uk

In keeping with our mission to educate as well as train, we have provided a little background information on Monet himself.

The instructions that follow are based on Corel PhotoPaint 8, but you can do much the same thing with any version of Corel PhotoPaint.

First you need to find a good subject. We have chosen this picture of a scene in Budapest.

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Creating the texture of an impressionist style is easy enough: one of the effects filters in PhotoPaint is designed to do just that. From the Effects menu, choose Artistic, 4 Impressionist.

To create a basic impressionist texture, check the Identical Values option for the Horizontal and Vertical Scatter slider controls, and then drag either of the two slider controls until you achieve the texture you would like to use.

The "blurring" effect of the early impressionist painters was much subtler than that of the later impressionists. You can re-create the style of either by increasing or decreasing the Scatter values in this dialogue window.

You could also experiment with non-identical values to create more individual effects. In the example right, we have chosen a fairly subtle effect, using a Horizontal and Vertical Scatter value of 9.

Monet was particularly fascinated by the way that a subject changed according to the different lighting effects created at different times of the day. Once you have created your basic Impressionist texture, you can experiment with different lighting effects using the Lighting Effects command in the Effects Menu.

From the Effects Menu, choose Render, 4, Lighting Effects

Check the Directional option, and drag the light source icon in the Preview window to an appropriate position for the effect you want to create. In this example, we have positioned it at the top left corner of the image, and set the arrow to point towards the bottom right corner of the image.

Choose an appropriate colour for the light source from the drop-down colour palette. We used a pale yellow in this example

Adjust the Brightness slider according to the effect you want to create

Click OK

This created a good strong sunset effect over the building at the front right of the picture, but we needed to have a red tint in the sky as well. Increasing the brightness would have allowed the colour to spread to the sky, but only at the cost of completely flooding the detail at the bottom front of the picture.

So we created an object from the sky using the Magic Wand Tool. An Object in PhotoPaint is like a transparent sheet of film applied over the image. Initially the Object is transparent, but you can vary the transparency, or Opacity of the Object using the slider control in the Objects Docker window.

Using the Magic Wand Tool set to a tolerance of 10, we were able to create a mask from just the blue sky in the image, from which we then created an object. A second Lighting Effect was then applied to the object rather than the entire image, using the same colour and brightness settings as for the first light source, but positioned at the bottom centre of the object.

The Brightness value was 87%, and the Cone size was adjusted to give a good spread of white light across the sky.

PPA runs regular courses on most of the products in the Corel suite of applications, and is an approved Corel Training Partner. Click here to see the CorelDraw Introductory course outline; here for the Advanced course outline; or here for the Corel Graphics Suite Introductory course outline that includes training on both CorelDraw and Corel Photo-Paint.

We also run courses for most popular office software, including Adobe PageMaker, FrameMaker, PhotoShop and Illustrator, QuarkXPress, and Microsoft Office. For details of availability and prices please contact us.

If you have any comments regarding this or any other page of this website, or if you have suggestions for future features on this Hints & Tips page, please contact webmaster@ppatraining.ie

Visit the Corel User web site at http://www.coreluser.com