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ProArtisan2

The complete ProArtisan2 manual

Process mode

This menu provides the interface to the image processing section of ProArtisan 2 and also to the very powerful Frisket facilities. The Filters and Effects arc described in functional terms in this chapter. The real power of the Filters and Effects is that they can be selectively applied to any discrete area of the canvas by using a frisket.

Clear Screen

Click on this menu item to clear the canvas to the current colour selected from the palette. Alternatively use Ctrl X at any time the program has the input focus. Frisket - when creating a frisket this option sets or unsets the frisket depending upon which colour is chosen in the palette.

Defining a Frisket

Before moving on to the next five items you need to understand what a frisket is. A frisket is used to protect an area of the canvas from change. You can then work on the canvas painting or manipulating anywhere except the area that has been protected with the frisket. With the Invert Frisket option you can reverse the frisket so that you can only paint or work on the area originally defined by the frisket. See page 21 for more explanation on a frisket.

Warning: A frisket requires additional memory equivalent to the size of your canvas. Once you toggle the Frisket Icon a frisket is created. If you do not need the frisket and want to recover the memory use Process -> Remove Frisket.

The Frisket icon has three states:

You can use Create Frisket instead of using the Make Last and Add Last items in the Process menu. For example you could plot a rectangle onto the canvas in this mode and it would appear as a red rectangle. When you toggle the Frisket icon to Frisket Active the red rectangle is no longer visible but if you try to draw onto the canvas the area covered by the rectangle is protected eg;

Note - The frisket is a tool, it does not alter the saved or printed image.

Remove Frisket

Clicking on this item removes the current frisket and recovers the memory used by it. A frisket requires the same amount of memory as your current canvas and so doubles the memory requirement. On machines with less than 4 megabyte of RAM you will be unable to use the frisket except on a canvas with a maximum size of half a screen.

Invert Frisket

Clicking on the icon, or pressing Ctrl I, inverts the frisket so that an area that is protected by the frisket becomes the area that can be worked on and vice versa.

Frisket Colour

Clicking on this icon sets the frisket colour to the current colour. This lets you set the frisket colour so that it is easily distinguished from the colours in the canvas.

Make Last

Click on this icon to make your last action the frisket. This applies to almost any action. For example, if you had filled an area then the filled area becomes the frisket when you select Make Last. Other useful friskets can be created after using Magic Brush to change colours selectively and then making the changed colours the frisket. You can even undo the last action after you have made it the frisket.

ProArtisan 2 has a a one step Undo feature, documented elsewhere, which allows you to delete operations and restore the previous screen. This 'back screen' is what is used in the Make Last and Add Last items. When you click on either of these items the program compares the 'back screen' with the canvas and any changes or additions to the canvas that do not appear on the 'back screen' are used to form the frisket. However, because you still have the 'back screen' you can choose to Undo the changes and revert to your previous canvas. The key thing to remember is that the changed areas are now stored in the frisket and can be used to protect areas on the canvas.

For example, you can achieve the same effect as shown previously by having Frisket Inactive and painting the X onto the canvas. Next press Ctrl L to make your last action (painting the X) into the frisket. Now click on Undo to remove the X and toggle the Frisket icon to Frisket Active You now have exactly the same effect as before. In some instances it is easier to use this method instead of Create Frisket directly - particularly if you wanted to create a frisket but had forgotten to turn it on.

Add Last

This is similar to Make Last above except that the frisket defined by the last action is added to any frisket that already exists, allowing you to build up a complex frisket,

Filters & Effects

Many of the entries in the Filters and Effects menus use a common slider box to set a percentage value. One box is described here to avoid duplication.

The slider can be altered either by dragging the black bar or by clicking on the bump arrows. The current value is shown between the bump arrows. The significance of the value is explained in each item. Click on OK to confirm the value and initiate the action. If you want to carry out repetitive operations use ADJUST to click on the OK button. In this case the effects are not cumulative as each click applies the effect to the 'back screen', which hasn't changed because the changes have not been confirmed. This enables you to fine tune the effects to achieve the required effect. For example a lighten by 20% might not be quite enough so you can then try 25% to sec if that is better.

Filters

This sub menu and the next contains a wealth of exciting options which are extremely versatile, particularly when used in conjunction with the Frisket or other Filters and Effects. The best way to appreciate these filters is to try them out on an image. You can use the same image in each case and then use the Undo option before moving on to the next filter. Be warned that some of the filters are processing massive amounts of data and so they may take a little while to complete but the effects are worth waiting for. On the more complex filters you can press Escape to abandon an operation and preview the effect as far as it has reached. The filters work horizontally down the screen. You can then use the Undo option and repeat the effect or alter the parameters in the knowledge that the effect will be what you require and thus worth waiting for.

You may like to use a small image for trying out some of these filters.

Inverse	Clicking on this item inverts the canvas colours logically, providing a colour negative effect. The canvas is still in colour. Technically the effect is NOT RGB and is created from the following formula - (255 - RED) + (255 - GREEN) + (255 - BLUE)
Tint	Click on this item to remove all colour from the canvas and turn the image into a tinted image using the current blend set. If the blend set is the grey scale then you will get a monochrome effect. Other sets will provide different tints. For example Blend set 2 gives a sepia effect. Watch out for Blend sets that have been destroyed by loading in sprites with arbitrary 256 colour palettes.
Lighten	This option has a sub menu, shown on the previous page. which lets you set the amount that a picture is lightened by adding a percentage to the grey level values of the current pixels. A value of 100 gives a totally white screen. Click on OK to lighten the image. Remember that you can use ADJUST to try successive changes.
Darken	This item is the opposite of lighten and the slider lets you set the amount by which a picture is darkened. A value of 100 gives a totally black screen. Once the value is set click on the menu entry to darken the image.
Cutoff	This item enables you to posterise the image. It changes the image to just two colours. The slider determines at which intensity the switch from one colour to the other takes place. The two colours used are those at either end of the current Blend set. The default Blend set is black to white and thus default action will use black and white. A value of 5 on the slider gives a totally black image with Blend set I. A value of 100 results in a totally white canvas with Blend set 1. Frisket - this item works in a similar way when creating a frisket. It is the only item in the Filters menu that works when creating a Frisket.
Contrast	This item applies contrast to the image. Contrast is the balance between light and dark. The larger the value the greater the contrast.
Anti-Alias	This item softens the image by blurring the edges so that objects merge into each other. The slider determines the accuracy of the colour selection method used but at the expense of speed. In most cases the default setting will provide good results in a fast time but some palettes require more accuracy and are slower as a result. The higher the accuracy value the longer the process takes. The setting of this slider also affects the Sprite Soft paste options and some of the Generic filters.
Remove Dots	This item is of most use on scanned or digitised images. Its purpose is to remove isolated dots in the image. The slider controls the target dot size. Large clusters of dots are anti-aliased, single dots are removed and replaced by their surrounding colour.
Colour Shift	This item enables you to alter the colour balance in an image. A small preview window shows the effect of the colour shift on the image. The canvas is not altered until you click on OK. The sliders in this window are Red. Green and Blue (RGB). They range from -128 on the left and 128 on the right with a mid point of zero. If you raise the red slider up towards 128 the image gets progressively more red because the red component is being intensified. Moving the slider to the left towards -128 progressively removes the red component and at -128 almost all the red is removed from the image. You cannot see the effect of the change until you release the slider. Remember, the canvas is not altered until you click on OK but you can preview the change in the small Preview window. Exactly the same applies for the other sliders except that they control the green and blue components. The row of blocks to the left of the OK button enable you to lock out areas of differing intensity. A block is selected when it is solid. If you only have one block on the left selected then the colour shift only applies to the darkest colours. If you add the next block then all colours up to that intensity are affected. You can have individual blocks selected so that you only affect one band of intensity. The block at the far right selects only the brightest intensities. You can apply a Colour Shift and then toggle the intensity blocks to see the effect that they have.
Grey Shift	This item first converts the image to a grey scale using standard algorithms and then processes the grey scale according to the gradient slope defined by the line in the dialogue window. On computers without a colour card the number of visible greys is 16 but on a colour card machine this can be up to 256 greys. The source grey scale lies on the horizontal axis and the resulting grey scale lies on the vertical axis. Black for each axis is in the bottom left corner. This all sounds very technical but as it is easy to try it you are best doing so and noting the effects. When used on images that are originally colour, the number of resultant greys depends upon the colour distribution in the original image. If you are trying to understand this filter you are best using the supplied image called Greys as the results with a grey scale image are much more predictable. The icons in the window are numbered above and their function is detailed below. Standard - The default line of a 45 degree slope leaves all the greys as they were. This is because all of the greys represented in each square on the horizontal axis are mapped to the corresponding square on the vertical axis. Posterise - This reduces the image to 5 colours 0, 25, 50, 75 and 100 % black signified by the five steps. Solarise at 50% - All the colours from black to mid grey are mapped to a brighter grey (except for black which stays the same) with mid grey converting to white. The line then goes down so mid grey becomes white and as you move further towards white in the original the greys become darker ending up with white on the original becoming black. Try it on the Greys image and re read the above. Posterise at 50% using 2 colours. This has the effect of reducing the Grey file to just two colours, black and white. All colours from black to mid grey are converted to black because there is no vertical component and all colours from mid grey to white are converted to white because the horizontal line is at the top of the vertical axis. This is the same as the Cutoff filter. Mid range boost - This has the effect of keeping black and white constant but brightening all the greys in between . Invert - This reverses the effect of any gradient already defined. As well as the supplied gradients you can draw your own into the grid by altering one of those already there. Grey Shift is useful for processing images that are to be printed in monochrome and is also very useful for manipulating 256 grey level sprites. You can for example boost some areas and reduce the effect of others.

Effects

This menu provides lots of special effects that can be applied to the canvas.

Emboss	This effect is quite amazing. It uses the current Blend set to create an embossed image on the canvas. Initially you should try it with the grey scale blends, set one. This feature can be used to make some interesting backdrops for your desktop.
Sphere	This item wraps the whole canvas onto an imaginary sphere. The first parameter controls the size of the sphere used and the second controls the distance your imaginary viewpoint is away from the sphere. These are represented by the sphere and square respectively.
Find Edges	This item uses the familiar drag box to set a value. When you click on OK this item attempts to find any edges that occur in the image. The value of the drag box controls the width of the edge on the resulting image.
Facet	This item replaces each colour by the most common colour in its vicinity based on a 3 by 3 grid. Try it and see.
Halftone	This item creates a fractal halftone which gives a more natural mezzotint type diffusion that avoids patterning normally associated with halftoning. The drag box controls the cluster size around which the fractal is based. A halftone consists purely of two colours. Normally the two colours are black and white which gives the appearance of grey scales. This effect uses the first and last colour in the currently selected blend set so to achieve black and white use Blend set 1. When used in conjunction with the frisket you can use Halftone to add random 'noise' to areas of the canvas before further processing. For example a Halftone followed by an Emboss gives new textures.
Magic	This item applies the settings in the Magic Brush dialogue in the Painting menu to the whole canvas.
Sharpen	Clicking on this item applies a sharpen filter to the image which sharpens up the edges and makes them harder. It is similar to the Emboss item but enhances the colours present rather than using the current blend set.
Pattern	This item leads to a Pattern dialogue window. The large area shows the current sprite. Depending upon the size of the sprite you will see part of it or the sprite repeated a number of times. This dialogue only has relevance if the sprite is repeated. To alter a value drag the sliders or click on the bump arrows. The sliders and bump arrows from top to bottom are:  Horizontal offset - which slides the repeated patterns horizontally to provide an offset between rows of the sprite.  Horizontal displacement - which opens up the horizontal gap between the sprite tiles. The white area will be transparent and show the canvas through it.  Vertical displacement - which opens up the vertical gap between the sprite tiles. The white area will be transparent and show the canvas through it.  Sprite orientation - the four P icons can be clicked on to alter the orientation of the relevant sprite tiles in the pattern. The sprite that is flipped depends upon the size of the original sprite. Clicking on the top left P icon will always flip the sprite to the right of the one flipped by the top left icon. To apply the pattern to the canvas click on the OK button.
Generic	This item leads to a sub menu dialogue window that has thousands of possible combinations for designing your own filters. A number of pre-defined filters are provided by clicking on the bump arrows to move through the list. You can either modify an existing filter, which have meaningful names, or go to the last filter titled Null/User and alter that one. The latter action is preferred as any changes to the existing filters remain in force until the program is run again. The two icons above the OK box provide Contrast and Brightness settings. The nominal base. or neutral position, for these is 128 for contrast and 0 for brightness.
Filter Design	This is a slightly more technical description of what the Generic Filter is and what it does. Most of the filters supplied in the Filters menu can be created using the Generic option. The filter is applied to every pixel in an image and the current pixel being processed is always at the centre of the matrix. The 3 by 3 matrix allows you to set weighting values that are applied to the pixel in the centre of the grid. Taking the example of the filter shown in the dialogue box above, the resulting pixel is made up of 4 units from the central pixel, I unit from each of the corners and two units from the centre pixels of each side. This then anti-aliases the image because the pixel retains more of the centre or original pixel than any others but is influenced by the other pixels to varying degrees. The following matrix sharpens an image by making the pixel 'stronger' than those surrounding it. All that we can suggest with this item is to experiment, but do keep a note of any particularly nice filters that you discover as you may want them in future. We would also be pleased to hear of useful filters. Block  This item converts an image into blocks by converting individual pixels into larger blocks. It gives the same effect as is seen on TV to hide a person's identity. It also brings back memories of graphics on the BBC micro. The slider controls the si/.e of the block.
Texture	This item is similar to the Texture option in the Paint menu, see page 25. Instead of having to paint an area the texture is applied to the whole screen. Textures are selected from the sub menu dialogue.
Crop to Window	This item performs a crop on the canvas. This means that areas are removed from the image to reduce the canvas to the si/e shown in the window. To perform a Crop scale the main window so that the portion that you want to retain is shown in the window and then click on Crop to Window. Note that you cannot retrieve areas thrown away by cropping so it may he sensible to save the whole image first as a safeguard. This facility has many uses including the cropping of scans to leave the required area.

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