Artefactual Skills for Simulating Impasto Effect in Digital Painting: An Adobe Photoshop Solution

Impasto is one of the fascinating techniques in studio painting that traces its foundation to the period between the 17 th and 19 th century Italian painters like van Gogh. It is characterised by thick application of paint in a plastering mode to artistically model forms on a canvas using either a bristle brush or a palette knife. When effectively executed, the technique finishes with the effect of ridges that cast shadows under grooves created by the thick application to give the painting its unique tactile contrasting appearance. In digital painting, the painterly effect of impasto is simply impossible to execute. Most of the well-known graphic application software cannot offer any applicator that can render the characteristic effect excellently. The author of this paper has developed a practical scheme for achieving this result using the Craquelure Filter in Adobe Photoshop version 21. The principal objective of the author is to employ the descriptive and demonstrational research methods to illustrate this artefactual scheme, which constitutes a practice-led exercise under the design-based research scheme. In this scheme, the author engages two of the major digital painting techniques: “Digital photo-art” and “Traditional digital painting” techniques to execute a figure painting composition in impasto style.


Introduction
One of the fascinating techniques in painting that require dexterity of skill to execute is the Impasto painting technique. The technique requires thick applica-tion of paint, a mode that often reveals the character of the tip of the applicator.
Painters sometimes mix the paint right on the canvas to derive the unique characteristic effect of impasto, an effect which leaves the painting with a textural finish that can be felt by touch and the visual impression of the dry paint peeling from the canvas. Oil paint is the traditional medium that has dominated this technique due to its thick consistency and slow drying rate. However, experimentation has shown that by increasing the body of gel in mixing acrylic paint, it renders it suitable for achieving impasto effect. The style that results from this mode of painting using oils or acrylic is more of impressionistic representation of forms than objective representation.
The internet today abounds with fascinating digital paintings (Bing.com, 2022) that prove the dexterity of new-media artists to use the computer as a tool for producing creative art works that march the aesthetic standard of works produce with traditional painting tools and techniques. Unfortunately, the uniqueness of the effect of impasto technique renders it technologically difficult to create with the computer. The closest this can be achieved is to camouflage a simulated visual effect that bears the resemblance of true impasto painting. Adobe Photoshop is equipped with a filter scheme that can help new-media artist to achieve this result after executing the digital painting in a particular procedure. This is the focus of this paper, which aims at demonstrating the author's practical procedures for achieving the effect of impasto in digital painting using Adobe Photoshop version 21.

Impasto Painting
Historical account reveals that the first objective for introducing this technique by masters such as Rembrandt, Titian, and Vermeer, was to represent folds in clothes or jewels (Wales, 2022). This was at its first emergence during the Venetian Renaissance where Titian and Tintoretto, created complex figurative scenes to explore how the sensuous properties of paint could convey light rippling off soft skin or cascading drapery. Titian's "Poesie" series including Diana and Actaeon, 1556-1559, demonstrated this mastery of his technique (Auerbach, n.d.).
The technique gained further prominence in the 17 th century, when some Baroque painters such as Rembrandt, Frans Hals, and Diego Velázquez skilfully and minutely used the technique to depict lined and wrinkled skin or the sparkle of elaborately crafted armour, jewellery, and rich fabrics. The 19 th -century painter Vincent van Gogh made notable use of impastos, building up and defining the forms in his paintings with thick, nervous dabs of paint. Twentiethcentury painters such as Jackson Pollock and Willem de Kooning often applied impastos with dynamism and a gestural bravura that emphasized the physical qualities of the paint itself. Since then, raw pigments applied thickly to a canvas have become a staple technique of modern abstract and semi-figurative painting (Chauhan, 2012).
Abstract expressionists such as Hans Hofmann and Willem de Kooning also or "mix", perfectly describes how these exponents applied paint in this technique (Wales, 2022).
The technique has inspired some contemporary painters of the 21 st century, to explore it in various experimentations for stylistic results. In Ghana, mention can be made of Ablade Glover who has extensively used it to address his compositional themes in crowded confines of hustling and bustling activities. He uses warm hues to painterly portray vibrant scenes of Ghanaian life that focus on women and mothers from Africa, market scenes, crowds and landscapes (Guirandou, 2022). As documented by Chili Hawes, director of October Gallery, Glover uses warm impastoed pigments to express the sun and heat of his country to depict animated landscapes that mirror the exuberant diversity of Africa: its bustling market stalls, brightly attired crowds, and the dynamic energy associated with Ghana (Hawes, n.d.).

Methodology of the Study
This research is a practice-led digital painting exercise. In this modern digital technological dispensation, Practice-led (Candy, 2006)  digital painting skills to fine art students in higher education (Annum & Poku, 2021). This underpins the essence for its adoption in developing this skill for the benefit of digital painters.
Demonstration Method: Demonstration (Teachmint, 2022) is a method in teaching and learning processes carried out in a very systematic manner to help students who have difficulty in connecting theories to actual practice or are un-able to understand the application of theories, gain better understanding of procedures. It is useful for the simplification of technical procedures developed by an artisan in any field of art under any practical pedagogical system. As a new-media art technologist exploring computer technologies for fine art painting, the above principles underlying Demonstration method, gives relevance to its usage to show the systematic step-by-step digital techniques for painting and simulation of the effect of impasto painting in Adobe Photoshop. Two of the major digital painting techniques: "Digital photo-art" and "Traditional digital painting" techniques (Annum, 2014) were employed to achieve this objective.
Descriptive Research Method: Descriptive Research method (Alhassan, 2007) is considered as one of the prevailing research methods of the behavioural sciences used to systematically investigate, examine, analyze and describe occurrences in the home, the classroom, recreational centres, offices and many other work places. It offers researchers the strategy for accounting for the status of a phenomenon under study by obtaining appropriate information that can best describe, interpret or explain the nature of a phenomenon. It is therefore the most appropriate research method for artists in studio-art practice who have to demonstrate to their readers, techniques and styles they employ in their practical activities to use to bring clarity to their discussions. This is the bases for adopting descriptive research method in this practice-led research to bring the technical procedures to the understanding of readers.

ESSENTIAL UTILITIES IN ADOBE PHOTOSHOP (Adobe Systems, 2013)
Adobe Photoshop, aside its dual functionality in creating and editing both bitmap and vector images, is embedded with filtration tools purposely for simulating variety of fascinating effects as it exists in easel painting to help digital artists, bring their digital paintings to the standard of traditional studio easel painting. It also enables designers to develop multiple stylistic ideas in digital painting (Annum, 2014).
Photoshop offers users the opportunity to work in any of the editing Colour Modes for changing colour values in images. It uses these modes to determine the colour model for describing and reproducing colours, and for displaying and printing images. The colour modes located in the image menu under the modes submenu ( Figure 1), include RGB (red, green, blue); CMYK (cyan, magenta, yellow, black); and L*a*b* (the "L" component being luminance or lightness, the "a" ranging from green to red and the "b" component from blue to yellow, as two chromatic components). It also includes modes for specialized colour output such as Indexed Colour and Duotone, which is used to increase the tonal range of a grayscale image by using different colour inks to reproduce different gray levels. It is important to note that Colour modes affect the number of channels and the file size of an image.
Photoshop also offers Colour Adjustments tools for adjusting the tonal levels, which include colour brightness/contrast, colour balance, hue/saturation of continuous-tone images and posterize adjuster. This is a very important working

Watercolour Filter
The watercolour filter is designed to transform an image or a painting in a watercolour style using a virtual medium brush, loaded with water and colour simplifying details. Where significant tonal changes occur at the edges, the filter saturates the colour. In the authors impasto simulation technique, this filter first helps to intensify patches of strokes which when filtered with the Craquelure texture simulates the visual effect of impasto.

Craquelure Filter
The Craquelure Texture Filter is designed to give an image the appearance of high-relief plaster surface, which produces a fine network of cracks that follow the contours of the image. When applied, it creates an embossing effect for images that contain a broad range of colour values. It is these capabilities that the researcher appropriates for simulating impasto effect in his digital paintings.

Virtual Tools for Impasto Painting
It is important to understand the researcher's choice and mode of application of the essential tools and adjustment commands in Photoshop for image enhancement and digital colour manipulation to achieve impasto simulation. The tools and commands are: 1) Posterize command; 2) Colour balance command; 3) Lasso Selection Tools; 4) Smudge Tool.
Posterize Adjustment Dialogue Box ( Figure 6) The Posterize command opens its adjustment dialogue box that lets you specify the number of tonal levels or brightness values for each channel in an image and then maps pixels to the closest matching level. This adjustment is useful for creating special effects, such as large flat areas in a photograph. It is useful for introducing variant colour schemes in digital images. The effect is more vibrant and interesting especially when the number of levels in the image is reduced.
The researcher uses this adjustment tool to change the colour scheme of the photograph to render it with a new colouristic effect for painting. This is the ad-justment tool he uses to convert photographs into fascinating paintings.
The posterize adjuster is selected from; the Image menu > Adjustments > Posterize to open the posterize dialogue box. The adjustment is effected by moving the slider to increase or decrease the value in the level editable box, which correspondingly alters the tonal levels.
Lasso Selection Tools (Figure 7) The lasso selection tools are three in all; Lasso, Polygonal lasso and Magnetic lasso.
The lasso and polygonal lasso tools let you draw freehand segments of the border of an image or to select a colour element or shape in an image. With the magnetic lasso tool, the border of an image snaps to the tool as you move the cursor along the border of an area in the image. The magnetic lasso tool is especially useful for quickly selecting objects with complex edges set against high-contrast backgrounds. Unfortunately, the Magnetic Lasso tool is not available for 32-bits-per-channel images.
Customising the Magnetic Lasso tool Before using the lasso tool, it has to be customized in the options bar to specify the selection mode and its sensitivity to the edges of the image. 1) Specifying a selection mode in the options bar is based on whether to create a new selection "A", add to an existing selection "B", subtract from a selection "C", or select an area intersected by other selections "D" (Figure 8).
2) The other options in Figure 9 determines the Feather and Anti-alias options, detection width, edge contrast, fastening points frequency and stylus pressure.    • Feather blurs edges by building a transition boundary between the selection and its surrounding pixels. This blurring can cause some loss of detail at the edge of the selection.
• Anti-alias smoothens the jagged edges of a selection by softening the colour transition between edge pixels and background pixels. Because only the edge pixels change, no detail is lost. Anti-aliasing is useful when cutting, copying, and pasting selections to create composite images.
Note: You must specify this option before using the tool. After a selection is made, you cannot add anti-aliasing.
• Width specifies a detection space. When a pixel value is entered for the Width, the Magnetic Lasso tool detects edges only within the specified distance from the pointer.
To change the lasso pointer so that it indicates the lasso width, press the Caps Lock key. You can change the pointer while the tool is selected but not in use. Press the right bracket (]) to increase the Magnetic Lasso edge width by 1 pixel; press the left bracket ([) to decrease the width by 1 pixel.
• The contrast controls the lasso's sensitivity to edges in the image. Enter a value between 1% and 100% for Edge Contrast. A higher value detects only edges that contrast sharply with their surroundings; a lower value detects lower-contrast edges.
• The Frequency controls the lasso's sets fastening points. Enter a value between 0 and 100. A higher value anchors the selection border in place more quickly.
On an image with well-defined edges, try a higher width and higher edge contrast, and trace the border roughly. On an image with softer edges, try a lower width and lower edge contrast, and trace the border more precisely. To use the Colour Balance dialogue box: • Make sure the corresponding layer in the layer panel or an image element is selected.
• Open the Colour Balance dialog box.  • Select each of the tone balance options (Shadows, Midtones, or Highlights) separately to select the tonal range on which you want to focus the changes. • For each selection, drag a slider toward a colour you want to increase in the image; drag a slider away from a colour you want to decrease in the image.
The values above the colour bars show the colour changes for the red, green, and blue channels. Values can range from −100 to +100.
The Photo Filter command can also be used to achieve similar result. The adjustment mimics the technique of placing a coloured filter in front of a camera lens to adjust the colour balance and colour temperature of the light transmitted through the lens in exposing the film. Photo Filter also lets you choose a colour preset to apply a hue adjustment to an image. If you want to apply a custom colour adjustment, the Photo Filter adjustment lets you specify a colour using the Adobe Colour Picker.

Smudge Tool
The smudge tool is the virtual applicator in Photoshop that the researcher uses to blend and spread colours on a surface to prepare an image for impasto simulation. The tool simulates the action of dragging a finger or a brush through wet paint. It picks up colour where the stroke begins and pushes it in the direction it is dragged. It is effective for retouching colours or blending tones of colours in an image. It is customised by using the brush preset picker, mode, strength and finger painting options.
The brush picker defines the character of the tip of the smudge tool. The harder the brush picker the more distinct the edges of the strokes appears and the better the result for simulating impasto effect. The normal smudging mode also creates the best result. The "strength" in this scheme specifies the volume of paint it drags per stroke of application. The higher the strength, the more distinct the stroke appears and vice versa. For best result, a moderately high strength between the values of 50% and 70% is recommended. The sample all layers option has to be excluded from the customisation schemes. The finger painting option is selected to enable the smudge tool to introduce new colour shades from the colour palette. Holding down the "Alt" key whilst the smudge is still selected will perform the function of applying the current colour displayed in the foreground colour box in the colour palette.
When the Alt key is released, it reverts to the smudging mode.
As the main virtual applicator for blending colours, the smudge tool has to be customised to possess the appropriate character for creating desired strokes for achieving the desired impasto effect. The researcher's technique is facilitated by the following schemes: Step 1. Select the Smudge Tool from the tools bar.
Step 2. On the Smudge tool options bar.

1) Select Hard Round Pressure Opacity from the "Brush Preset Picker"
and adjust the size of the tool to a value between 20 pixels & 30 pixels for the paper size of 600 pixels longest dimension. 2) Select "Normal" in the Mode.
3) Specify a value between 50% and 70% in the Strength. 4) Uncheck "Samples cloned data from composite data" "Finger Painting" and Pressure for size icon .

5) Click Toggle the brush settings panel icon to open the Brush Preset
Wizard and customise the "brush tip shape" as follows: a) Check ONLY Shape dynamics box, all others MUST be unchecked. f) Check only "Flip X" and "Flip Y" excluding Brush Projection. This will force the tip of the smudge tool to tilt along those angles whilst smudging.
g) Click the padlock to the right-side of the shape dynamics to lock the settings.

Results and Discussion
The author's impasto simulation technique is based on a digital photograph of a composition as his sketch model. The old tradition of easel painting enjoins fine artists to sit in the scorching sun to sketch from nature, transfer unto a canvas before colour pigment is applied to produce a painting. With advancement in computer systems, smart phone and digital camera technologies, this laborious procedure has to give way to easier schemes like capturing sceneries of interest with digital camera devices and importing them into graphic application software as models for developing compositions. Using the digital camera to capture images for digital painting in Adobe Photoshop is fast and less laborious to execute. This is because the complexity in colour pigment orchestration and mixing on a palette plate, as well as the unbearable emission of toxic fumes from solvents is non-existent since the software offers millions of colour shades to work with.
The digital procedures discussed in this paper should not be regarded as a standardised blueprint, but fundamental artefactual scheme to help digital painters in advancing their own techniques for achieving similar results. The flexibility of Adobe Photoshop application tools makes this a possibility.

Painting Procedures
Step 1: Setting new pixel dimension for the sketch image Ones the photograph to be worked on is opened in Photoshop, it must first be resized into smaller pixel dimensions. This is very vital for maintaining a freeze-free working system. The width or height dimension of the image has to be set at a pixel dimension of not more than 600 pixels. Figure 11(a) is the original photograph serving as the sketch from which the sample image ( Figure   11(b)) for this demonstration was cropped and resized.
To edit the image size, go to image menu > image size to open the image size dialogue box. It is important to ensure that the resample image box is checked as well as the constrain proportions box. The resolution has to be 72 pixels per inch, with any of the image dimensions not more than 600 pixels. This is to help prevent the computer from freezing when colour application begins. The cropped composition (Figure 11(b)) was slightly edited with the smudge tool as a matter of choice, to modify the form. This had to do with the neck of the mother in the composition. It was purposely to enhance the pose of the woman (Figure 11(c)).
Step 2: Selecting picture elements with the magnetic lasso tool: 1) Select the magnetic lasso tool (Figure 7).
2) Carefully click the border of the image (Figure 11 6) To switch temporarily to the other lasso tools, do one of the following: • To activate the lasso tool, hold down Alt and drag with the mouse button depressed.
• To activate the polygonal lasso tool, hold down Alt, and click. 7) To erase recently drawn segments and fastening points, press the Delete key on the keyboard until you have erased the fastening points for the desired segment. 8) To close the selection border: • Double-click, or press Enter or Return to close the border with a freehand magnetic segment.
• Hold down Alt and double-click to close the border with a straight segment.
• Drag back over the starting point and click to close the border. Step 3: Optimising with Colour Balance and Posterize Commands.
The colour scheme of the selected picture elements (Figure 12) has to be optimised (Figure 13(a)), with the Colour Balance command ( Figure 10) as a matter of choice before the posterize command ( Figure 6) is used to break the continuous photographic tones into levels of large flat areas (Figure 13(b)). This is achieved based on the number of levels specified in the posterize dialogue box.
For this exercise, eight (8) levels was specified.
Step 4: Using Smudge Tool to Apply and Blend Colours (Figure 14(a)) Whilst the body areas were still selected, the Select Menu > Inverse, (Shift + Ctrl + I) had to be activated to select the cloth and background areas. In Photoshop, the colour palette provides millions of colour shades to be chosen for application using the smudge tool. Technically, the smudge tool can be used to apply colours and blend colours as well. The colour balance adjustment dialogue box can also be used to optimise the coloristic effect of the image as the smudging progresses.
1) In this process, the finger painting option of the smudge tool was G. Y. Annum activated to enable application of colour shades and tints from the colour palette. As the colours were applied, the strokes were loosely blended simultaneously in a swiping motion, maintaining the roughness of the strokes (It is important to use broad hard edge strokes and ensure that the strokes directions are visible when zoomed in and out. This is paramount for achieving desired result. Any hard round brush tip of size between 20 & 30 pixels is appropriate for producing distinct strokes on a canvas size of not more that 600 pixels on any dimension. Note that, the more noticeable the strokes appear, the better the impasto simulating effect will be).
2) Zooming In and Out of the image by holding down the ALT key on the keyboard whilst scrolling the mouse, makes it possible to smudge minute details.
3) The inverse command was activated again (Shift + Ctrl + I) to select the body areas before blending the posterized flat tones. At this stage, new colour shades and tints were introduced as a matter of creativity to enhance the colouristic effect of the image and to help in modelling the figure (Figure 14 The smudging was done using swiping motion strokes, executed in varied directions.
It is important to note that any deliberate attempt to blend the strokes with any soft round tip smudge tool to achieve smooth finish will adversely affect the impasto rendering. To tackle minute details, the size of the smudge tool has to be reduced below 20 pixels depending on the size of the minute area. Zooming In and Out by holding down the ALT Key on the keyboard whilst scrolling the mouse is essential for smudging minute areas.
Step 5: Impasto Simulation Two filtering procedures were used in this scheme: Watercolour Filter under Artistic and Craquelure Filter under Texture. The selection of the skin elements was first removed so both the skin and the background will be treated at the same time.
Watercolour Filter (Figure 15) Technically, the watercolour filter simplifies details by repainting an image in a watercolour style using a medium brush loaded with water and colour in a virtual state. Where significant tonal changes occur at the edges, the filter saturates the colour. The technique causes paint to build up along the edges of the brush stroke that displays broad range of colour values. It also enhances the distinctiveness of the individual smudged strokes, which is paramount in achieving impasto effect. This effect is the motivation for employing the watercolour filter as the preliminary process for preparing an image to be rendered with the Craquelure Filter to achieve impasto finish.
In the filter dialogue box, the shadow intensity and the texture sliders were reduced to the lowest default values of 0 & 1 respectively. It is only the brush detail slider that was adjusted to control the amount of paint that builds up along the edges of the brush stroke. In the filter dialogue box, the crack depth slider was reduced to the lowest default value of 0, whilst the crack spacing and crack brightness sliders were adjusted to enhance the impasto effect.  Figure 17(c) on the other hand is not a digital painting but an impasto painting, resulting from Prof Ablade Glover's traditional impasto painting technique. Glover is a renowned Ghanaian impasto painter who employs "wet-on-wet" and thick application of paint pigment on canvas to produce his impasto paintings characterized by lusciousness and dramatized result (Moller, 2022). By the author's personal acquaintance with Glover, it can be confirmed that his favourite painting applicator, the palette knife, enables him to achieve his swirling impasto effect, which is similar to the author's swiping technique of colour smudging.

Finished Result
The visual effect of the author's digital paintings (Figure 17

Conclusion
The fascinating characteristic of impasto as a style in studio painting makes it challenging to tackle in digital painting. The closest effect a new-media artist can realise is to simulate the effect as shown in Figure 17(a) & Figure 17(b). This paper has demonstrated that it will take skilful research to device a scheme in any graphic application software to render this result. Adobe Photoshop, which has been the software for this research comes with intricate tools for drawing and painting. It is however not equipped with any brush or palette knife for painting to achieve this style. The digital procedures discussed in this paper are the result of the author's seventeen (17) years experience in digital painting, exploring artefactual skills in developing schemes to render his digital paintings with the same visual qualities as easel paintings possess. His scheme for simulating impasto effect should therefore not be regarded as a standardised blueprint, but a fundamental artefactual scheme to help digital painters in advancing their own techniques. The flexibility of Adobe Photoshop drawing and painting tools makes it possible to explore other schemes to achieve similar effects.
The procedures demonstrated are only to serve as a basic manual for using: 1) The lasso tool for selecting picture elements.
2) The colour balance adjustment dialogue box for adjusting tonal levels in an image.
3) The posterize adjustment dialogue box for creating large flat tones for building colour schemes.
4) The smudge tool for applying and blending colours.
5) The filter gallery for the simulation of impasto effect in a digital painting.
The motivation for conducting this research has been to create basic technological procedures in Adobe Photoshop for enriching both amateur and professional fine artists with the needed skills for achieving impasto finish in digital painting.

Conflicts of Interest
The author declares no conflicts of interest regarding the publication of this paper.