This tip is going to discuss some Studio Artist features useful for building up tone in an image. Tone or mass can be thought of as representing the visual weight of a sketch or artistic rendition and relates to building some kind of representation of the original source luminance in the artistic rendition of that source image.  In this tip we’ll be looking at paint synthesizer and image operation features that are useful for this topic.

Visual perception of imagery can be thought of in terms of different visual sensory modalities. People’s perception of visual imagery can be broken down into raw visual components like line or edge, tone or mass, color, movement, etc. We perceive these component aspects of visual imagery when we examine an image or painting.  And artistic representational techniques take advantage of this by how they work to represent (or ignore) these visual sensory components.

Tone or mass in a sketch works to represent the low spatial frequency luminance of the original source image being recreated in a sketch. A sketch may try to accurately reproduce the original luminance values, or it may radically distort the original tone values to accent certain image features while ignoring or suppressing others. Tone or mass in a sketch can also work to accent positive and negative space in the original source image. Or it may be distorted to better reproduce or enhance certain edge structure or salient visual features in the original source image while acting to simplify other non-essential source image features.

Many Studio Artist paint presets work by adding visual information to the working canvas. A simplistic view of this process is piling on paint strokes until some stopping point is reached. If the artistic goal is simply to build up an artistic representation by working with colored paint strokes that clone the original source image and completely fill the canvas then a user can ignore more advanced strategies for building tone and just let the paint synthesizer pile on paint strokes until a successful stopping point is reached.

But assume you are building a black and white sketch.  If one blindly piles on black paint strokes eventually the entire canvas will be filled with solid black. So for this kind of artistic image a more intelligent paint strategy must be programmed within the paint synthesizer so that the paint preset understands tone and tries to reproduce it within the black and white sketch.

There are various visual intelligence features in the paint synthesizer that can be turned on and will then work as an aid in reproducing tone in a sketch. This includes features in the path start, path end, and path application control panels. Some of these features are probabilistic in nature. Others are more intelligent and visually compare the original source mage with the existing working canvas to determine if adding a new paint stroke in a particular area of the canvas will lead to better or worse tone reproduction. The path start controls work to intelligently position paint paths to best reproduce source tone. The path end and path application controls work to stop drawing a particular paint path if it’s going to lead to bad source tone reproduction in a rendition.

Different attributes of a paint preset can also be modulated based on the original source luminance as an aid in reproducing tone or mass in a sketch. For example, the brush size can be modulated based on the source luminance so that larger brush sizes are used to reproduce dark tones while smaller brush sizes are used to reproduce lighter source tones. A similar kind of modulation can be used for the path length of paint strokes. These kinds of paint synthesizer programing can lead to paint presets that intelligently try to adjust how they draw to reproduce tone in an artistic rendition.

Path Start Control Panel

Setting the Inv Gray Prob Weight option for the Probability parameter will lead to paths starting more frequently on darker areas of the image and less frequently in lighter areas of the image.

The Lum Range parameters can also be used to restrict path start locations to a specific range of source luminance values.

Path End Control Panel

The Visual Error parameter provides a number of intelligent options that can be used to build tone rendition in a paint preset. White and black canvas lum error assume you will be starting with a white or black canvas. The last 2 options make no assumptions about the initial canvas state.  All of these options will end a path from drawing if they feel that continuing drawing would lead to incorrect tone reproduction.

There are also path end luminance range  options like those discussed for path start. The difference is that they end a path if the path leaves the retricted luminance range.

Path Application

The Probability parameter in the Path Application control panel includes a number of different options that can be used to intelligently build tone. These include WhiteCanvasProbErr, WhiteCanvasErr, BlackCanvasProbErr, BlackCanvasErr, Paint Lum Err, and Source Image Lum Err. This probability control acts to drop out or restrict individual paint nibs from drawing based on it’s specific setting while an overall path is being painted.

The tone mapped sketch image above was generated by auto-drawing with the Default : Auto Sketch : Visual Model2 paint preset. This preset uses a WhiteCanvasErr option for the Probability parameter in the Path Application control panel. It also uses a WhiteCanvasLumErr option for the Visual Error parameter in the Path End control panel.

Preprocessing the Source Image

An alternative approach to building tone with the paint synthesizer is to preprocess the source image and then paint the modified source. The processing can act to accent certain tonal areas while suppressing others.

The example above shows a modified source image that was processed with the Threshold ip op using the Soft LA Threshold algorithm. Generating a paint sketch off of this modified source image would enhance hatching in the dark areas of the image while suppress hatching in the lighter areas of the image. So the final sketch tone map will not accurately reflect the actual source luminance values but will reflect the distorted modified source tone map.

Movie Pixel Index Background Textures

The background texture control panel of the paint synthesizer includes a very useful tool for building hatching patterns that are used to reproduce tone in a sketch. A movie background texture generates the background texture based on individual frames in a movie file. How the individual movie frames are indexed or accessed during drawing can be modulated based on various visual attributes.  These include the source image rgb or luminance values, which would mean that the movie frame that best reproduces a particular area of the source image would be used when drawing in that associated area of the canvas.

The normal movie background texture re-indexes the movie frame every time the paint brush moves through the complete local area associated with the background texture. So if the movie background texture was 64 by 64 pixels then after the paint brush moved 64 pixels the movie frame used for the background texture would be re-indexed.

Movie pixel index background textures re-index the movie frame for each pixel when drawing.  This has the potential to run slower, especially if the movie is drawing from disk rather than from a memory preload.  But the movie frame is adjusted for each pixel to accurately track whatever frame index modulation has been chosen.

So, you can use movie pixel index background textures as a sophisticated technique to build customizable hatching patterns that accurately reproduce source luminance or tone for each pixel.  To do this, you build a stack of hatching patterns that reproduce tone for different luminance levels. The patterns should additively build to reproduce tone. Source luminance is then used to modulation the movie pixel indexing when drawing takes place.

Two examples of this approach to building intelligent hatching for tone reproduction in a sketch is shown above and below. This image was generated with the Circle Hatcher paint synthesizer preset which is located in the Default : General category.

For more information on working with movie pixel indexed background textures check out this tutorial.

Sketch Mass Ip Op

The Sketch Mass ip op is a new image operation effect in Studio Artist 4. This effect can be configured to create  a wide variety of different tone or mass sketch effects. There’s another Sketch Edge ip op that focuses of generating edge and feature sketches. Using the 2 effects together in a paint action sequence (PASeq) gives you the power to create an infinite variety of different sketch effects.

Both Sketch image operations can generate raster sketch images or they can generate a set of bezier paths to define a sketch. The generated bezier paths can then be used to drive the paint synthesizer leading to an even greater range of potential sketch styles.

The tone sketch examples at the beginning of this section and at the very top of this tip were created using the Sketch Mass ip op.

The Sketch Mass ip op is described in greater detail in this tip.

Generating bezier paths is described in greater detail in the tip.

There are a wide variety of different tools available in Studio Artist for converting raster images into bezier path renditions of the image. These include techniques to generate bezier path edge sketches (like above), as well as bezier mass sketches based on cross hatching, and complete cartoon style vector renditions of of color imagery. This tip will provide an overview of different approach to generating bezier renditions of raster images.

The example above is a bezier path edge rendition made from the raster image called ‘model’ in the ‘a few source images’ folder provided with Studio Artist. The bezier paths were generated from the source image by running the Path : Generate Paths : from Source Edges menu command.

The generated paths are stored in the current layer’s bezier path frame after they are generated. The bezier path frame is a hidden buffer associated with each layer that can store and display a set of bezier paths. You can view the current layer’s bezier path frame by switching to bezier operation mode. Once in bezier operation mode you can also manually edit the individual bezier paths or hand draw new ones.

Each layer has it’s own bezier path frame. Any path menu operations that generate or modify bezier paths are doing so to the current layer’s bezier path frame. Keep in mind that if you are generating new bezier paths you probably want to initially erase the existing contents of the current layer’s bezier path frame prior to generating new bezier paths. You can either use the erase path layer command menu to do this, or shift clicking the erase button in the main operation toolbar will also do this when it resets the canvas to a default coloring.

Generate Paths

There are a large number of different Generate Paths menu options in addition to the one used above. Adjacent edges generate a bezier path on each side of an edge. Skeletons are bezier paths generated at the mid points between 2  edges, and are an attempt to represent the center spines of different image regions bounded by edges.

The NonWhite options are useful to convert a raster edge image into a set of associated bezier paths. For example, you might use some image operation or MSG preset to generate a black and white raster image edge rendition where the edges are black an the background is white. The NonWhite generate path options can then be used to convert than raster canvas image (or selection) into a set of associated bezier paths.

The Generate Paths : from Ip Op menu option is a new version 4 feature that can generate bezier paths from associated image operations.  not all image operations can generate bezier paths. If a specific image operation can generate bezier paths then this from Ip Op menu will be active when that image operation is active in the image operation editor. Image operations that support generating bezier paths include the Sketch Edge, Sketch Mass, and Color Edge.

Path Layer Commands

The Path : Path Layer Commands menus shown below provide a number of different tools that can be used to modify or enhance generated bezier edge renditions of sketches.

For example, running Size Prune , Connect if Close, and Simplify Lite menu commands on the initial bezier sketch of the model shown at the top of this tip results in the following set of bezier paths. Note how these modified bezier paths have a more stylized hand drawn appearance than the original set of bezier paths derived from the raster source image edges.

Sketch Image Operations

The Sketch Edge and Sketch Mass image operations are new to version 4 and can provide for a wide range of different sketch effects derived off of raster source images. While the normal operation of the 2 Sketch ip ops generate raster sketch images, as discussed above you can use the Path : Generate Paths : from Ip Op menu to generate a bezier path rendition of the associated Sketch effect.

The image below is a screen shot of a set of bezier paths generated using the Sketch Mass ip op and the Path : Generate Paths : from Ip Op menu command.

Once you have a set of bezier paths generated that represent a raster image, you can then paint in those paths using the paint synthesizer. This additional step allows for an infinite variety of different artistic styles to be created off of a given set of bezier paths. The bezier path images above are actual screen snaps of the canvas taken displaying the bezier paths when in Bezier operation mode. But you could generate identical raster canvas images by using a simple 1 pixel black line paint synthesizer preset.

For example, the image below shows a set of bezier paths generated using the Sketch Edge ip op displayed on top of a watercolor paint synthesizer rendition of those bezier paths.  A watercolor paint preset was initially selected and then used to paint the bezier paths by running the Path : Paint Paths : Full Layer menu command. This is an example of painting in a set of vector bezier paths with a raster paint effect into a raster canvas for raster image output.

Vector Output

The Studio Artist 4 paint synthesizer allows for vector paint effects. So you could take the initial bezier paths defining a sketch and then render them using vector paint strokes in the paint synthesizer. Or you could render them by drawing them in with raster paint effects. Vector paint strokes allows for tight anti-aliased renditions as well as resolution independent output. Raster paint strokes allows for organize paint textures, wet paint effects, smear and smudge effects, etc.

For example, the sketch image above is a vector eps sketch rendition of a raster source image of George Carlin. It was generated by first running the Path : Generate Paths:  from Source Images menu.  This generated a bezier edge sketch from the raster source image. That set of bezier paths was then painted in with the paint synthesizer by running the Path: Paint Paths : Full Layer menu command shown below.  This menu command paints in the set of bezier paths in the current layer’s bezier path frame using the current paint synthesizer settings.

For this particular example, i used a paint synthesizer preset that is capable of vector drawing and eps output of the associated vectors. Each bezier path is actually rendered as a bezier region by the paint synthesizer preset used for drawing the bezier paths, where the shape of the generated region defines a simulation of a paint or ink stroke that varies in width over the course of the path drawing. Because the final output was a vector eps file, the sketch is resolution independent and could be printed at extremely high resolutions or large print sizes if desired without losing any detail in the print.

When outputting vector artwork in Studio Artist 4 you can choose between eps, pdf, and svg vector formats. Note that in the example above the initial bezier paths have actually been converted into bezier shapes or regions that the user interprets as thick paint strokes in the final artistic rendition.

Additional Information

There are some additional tips that discuss generating and working with bezier paths and the various vector output formats.

For more information on generating EPS vector files, check out this tip.

For more information on generating and outputting SVG vector files, check out this tip.

For more information on the new Sketch image operation effects, checkout this tip.

For more information on things you can do with bezier paths in Studio Artist check out this tip.

To learn more about how to generate paint presets that do vector drawing check out this tip.

The Vectorizer is a completely different way to generate bezier region renditions of raster source images that was not discussed in this tip. For more information on the Vectorizer check out this tip.

There are 2 new Sketch image operations (ip ops) in Studio Artist v4. These 2 ip ops are sophisticated processing effects that can be used separately or together to build a wide range of different black and white sketch effects. The Sketch ip ops can either be used to directly create raster sketch effects or to generate bezier paths that can then be used to drive the paint synthesizer.

The new Sketch ip ops in v4 are called Sketch Edge and Sketch Mass. Sketched imagery is typically generated by using thin drawing strokes to build up a representation of a source image. Representing a source image in a sketch with line vs mass has been an established artistic technique since the days of Leonardo da Vinci. Line referring to the edge structure of the image (high spatial frequency). Mass referring to the underlying luminance structure of the image (low spatial frequency). 

These 2 representational components are encapsulated into the Sketch Edge and Sketch Mass ip ops. Sketch Edge is primarily about generating sketches that representing edge structure in a source image. Sketch Mass is primarily about generating sketches that represent source luminance (or mass) via different hatching techniques. Both Sketch ip ops are capable of generating tight or loose or very abstract sketches of a given source, depending no how their editable parameters are adjusted.

The sketch example shown at the top of this tip was actually created with 2 different Sketch Mass presets min composited together.

Sketch Edge

The Sketch Edge Editor control panel is shown below. A radically large number of different sketch effects can be generated depending on how you adjust these editable parameters.

A processed example from the above Sketch Edge parameter settings is shown below. Note that these paramters generate a fairly tight representation.

To loosen up the representation, a different EdgeLook can be chosen. 

For example, changing the EdgeLook to Simplify Extreme will generate the following processed example, which has a looser visual appearance.

Depending on how you adjust the editable parameters you can radically change the visual appearance of the sketch effect, from very representational to very abstract. The example below is a very different rougher sketch style.

It was created with the following parameter changes.

The Smart Triangle Edge Look setting generates a fairly abstract sketch based on using sketched triangle shapes. The Bloom+Edge PostEFX setting in combination with the On1 Finish setting create the burned out stroke appearance, which is very different than the first 2 examples that have a smoother pencil sketch appearance to the line strokes that make up the sketch.

Colorizing a Black and White Sketch Image

You can use the Colorize Ip Op to subtly colorize a black and white sketch with the colors from the source image. Here’s an example of a colorized version of the last black and white abstracted sketch effect.

The Editor settings for the Colorize Ip Op used to generate the above colorized sketch are shown below.

The Image Source is what will be colorized by the effect.  We chose the IP Source, which is set to the Current Layer. Whatever is in the canvas current layer will be colorized with these settings.

Now we need to choose where the color is coming from, which is determined by the Color Source setting. We chose Source for the Color Source setting, which means the color used for the colorization operation is coming from the Studio Artist source image.

Different Color Space settings will generate different colorization effects. You should try different ones to determine what colorization effect you like the best for your particular sketch image.

Sketch Mass

The Sketch Mass Ip Op can generate a large number of different sketch effects that try to represent the underlying mass of the source image being sketched. Since sketches are composed of thin lines, mass is represented using different hatching patterns. Sketch Mass can try to accurately reproduce source mass or luminance, or it can work in a more sophisticated way that mirrors how a human artist would try to represent positive and negative space in an image (as opposed to blindly reproducing luminance) which can lead to more natural looking sketch effects.

The example above was generated with the following Sketch Mass settings. The particular hatching pattern used in the sketch is generated by the BullsEye Hatch setting.

A looser sketch can be generated by changing the Hatch and EdgeLook settings, as shown below.

The following Hatch and EdgeLook setting changes were used to create the modified sketch above with the looser appearance.

Changing the Mass setting changes the way the effect models the source mass and can potentially change the appearance of the mass sketch quite a bit, as seen in the example below.

The settings for the example above are shown in the screen snap below. The Mass option was changed from Pos-Neg to SLA FixThres. The EdgeScan was changed from Default to Maximize Length. This new Edge Scan setting tries to maximize the length of the strokes by attaching adjacent ones, and you can see the results in the overall appearance of the sketch, which seems to have fewer sketch lines that are longer (as compared to the previous example).

Generating Bezier Paths

Both Sketch Edge and Sketch Mass can also be used to generate a set of Bezier paths, as opposed to their normal operation which generates a raster image as the sketch effect. To generate a set of Bezier paths, you would run the new Path : Generate Paths : from Ip Op menu command. If either of the Sketch ip ops is the current ip op, then when you run this menu command they will generate a set of bezier paths that represent the sketch effect they are generating and add them to the current layer’s Bezier path frame.

The generate paths from ip op menu command is a new feature in version 4. Not every ip op offers this functionality, so if the current ip op is not one that offers an option to generate Bezier paths then the menu will be disabled.

The generated Bezier paths are added to the existing contents of the current layer’s Bezier path frame. So you would generally want to erase the existing Bezier path frame before running a generate paths menu command. You could either do this by adding an erase path layer menu command as a prior step in a PASeq, or you could turn on the Erase before Action path layer record option menu flag before running the generate paths menu command.

Once you have generated a set of Bezier paths for your sketch effect, you can then use any paint synthesizer preset to draw them in an infinite variety of different paint styles. To do that you would first select the particular paint preset you wanted to use to draw in the Bezier paths associated with the sketch. You could then run the Path : Paint Paths : Full Layer menu command. 

Generating Vector Sketches as SVG or PDF files

Studio Artist 4’s paint synthesizer has a number of new vector output features. You can use these new vector paint features in conjunction with the Bezier path generation step discussed above to generate full vector output for your Sketch ip op effects. This can be especially useful for high resolution printing since SVG or PDF files are resolution independent and can therefore be scaled without any information loss for printing on very high resolution printers.