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David Gell's Blog

...a Painter brush maker and explorer who likes to share

November 2007 - Posts

  • Soft Grain Colorize

    In Painter, Soft Grain Colorize can be found in the Eraser method subcategory of the brush controls. In this article, we will be taking a closer look at this subcategory, and there is an associated brush library available for downloading at the end.

    Before we go any further, I will recap on some of the properties of this algorithm mentioned and used in the previous two articles.

    • The Soft Grain Colorize (SGC) algorithm allows us to simultaneously apply both the main and additional colors selected in the Colors palette, which in turn are influenced by the luminosity of the currently selected paper texture.

    • When used with high contrast paper textures, and painting at 100 percent opacity on the canvas or default layer, the painted regions corresponding to white paper texture areas will be covered by the main selected color in the Colors palette (even if that color is white). However, by painting on a layer with the composite method set to Gel or Multiply, transparency corresponding to the white areas of the paper texture is again achieved (although tinted by selected main colors or values other than white).

    • If the additional color is set to black, and the main color to white in the Colors palette, there is a direct WYSIWYG relationship between the imagery viewed in the Paper Preview Window of the Papers palette and that rendered by the custom variant used. This means that the results of changing paper brightness and contrast settings in the papers palette may also be previewed before making the stroke.

    • A little known feature of the Soft Grain Colorize algorithm is that by setting the Paper Contrast to 0 percent (no grain visible), with the additional color set to black and main to white, the Paper Brightness slider can be used as a near linear 'grayscale' value picker. In this case, the value displayed in the Paper Preview Window will also correspond to that rendered by the variant at 100 percent opacity.

    Using the Paper Brightness Slider as a Near Linear Saturation and Value Picker

    I want to elaborate further on this, as many Painter users have expressed concern that due to the current size of the Saturation/Value triangle in the Colors palette, it is difficult to accurately pick sat/val points which are close together. Although it can only be used with SGC based variants, the method I'm going to demonstrate could be a useful workaround. The method involves setting the Paper contrast to 0 percent, and using the main and additional colors as the two extreme sat/value points required. The Paper Brightness slider is then used to select saturation and values between these two points.


    In the example above, the paper brightness slider is being used as a 'grayscale' value picker, in this case using 25 percent paper brightness increments. The custom SGC Hard Basic Round variant was used to lay down the swatches, with brush opacity set to 100 percent.

    Note that by setting the Additional color to black, and the Main color to white, the value in the Paper Preview Window closely corresponds to that laid down by the variant at any given paper brightness.

    Moving the Paper Brightness slider to the right increasingly shifts towards the Main Color/value selected in the colors palette, whilst moving it to the right shifts towards the Additional Color/value.

     

     
    In this second screenshot, using the same hue values for both additional and main color in the colors palette, I have selected two sat/val points fairly close together. The resulting swatches were then laid down at 10 percent paper brightness increments.

    By holding down the Option/Alt key, I was then able to sample the HSV values of each swatch and read them in the Colors palette. The results were not perfectly linear (also incorporating a 1 percent hue shift), but were certainly more accurate than attempting to select them in the Saturation/Value triangle directly.

     

    Color Mixing 

     
    When attempting to mix two differing hues, the findings were less satisfactory, with best results being obtained with adjacent hues selected from the Hue Ring in the Colors palette. For example, when blue and yellow (opposite hues) were selected as main and additional colors (both at full saturation), there is a strong tendency for desaturation towards neutral gray as mixing progresses to 50 percent paper brightness. However, mixing say red and yellow (close hues) at full saturation yields virtually no saturation loss as in this screenshot.

     

    Using SGC Variants with a Rendered Dab Type

    In the brush library download which accompanies this article, there are several variants (mostly in the Pen and Ink category) which include the word 'Ren' in their name, signifying a Rendered dab type. To use these specific rendered variants in the same way as outlined in the previous section, it is necessary to first select a totally black custom pattern. Creating such a pattern is quite simple;

    1.  File> New and create a new document 8 x 8 pixels at 72 ppi.

    2.  Fill the canvas with black (HSV 0,0,0 percent)

    3.  Choose Capture Pattern from the Patterns palette flyout menu.

    4. Name the pattern Black in the Capture Pattern dialogue, before clicking O.K.

     

     
    For the rendered dab type, it can be seen that although the Eraser Subcategory is still Soft Grain Colorize, the Source is set to Pattern As Opacity. In some ways, these are competing algorithms, which may explain why we need to first load a completely black pattern in order to have no occurrence or detrimental effect of pattern opacity in our brush stroke.

     

    In actual fact, there are at least four different modes in which the custom rendered (Ren) SGC variants may be used in. The examples below will demonstrate that without adjusting any Colors palette or Brush controls settings, it is possible to render with the same variant;

    1. Both currently selected pattern and paper texture.

    2. The selected pattern without paper texture.

    3. The selected paper texture without the current pattern.

    4. Flat color based on the selected main and additional colors in relation to the Paper Brightness slider setting.

    For example;

     

     
    In the above screenshot, the resulting brush strokes were made in single passes with the custom SGC Ren Graphic Brush using firm stylus pressure. Multiple passes over the same area result in the stroke exhibiting the paper texture only, as this dominates over the pattern source by means of total cover.

    Note how the color value changes by adjusting the paper brightness slider. The opacity in the stroke is governed by luminosity within the pattern.

     

    For this second example, I have set the Paper Contrast to 0 percent in the Papers palette, which effectively removes the presence of paper texture to leave just the re-colored pattern imagery.

     

    Here, I have loaded the custom Black pattern to effectively eliminate the occurrence of the pattern in the brush stroke. The paper contrast  value has been increased to 100 percent in order to make the paper texture visible in the stroke.

    Note how the luminosity of the new pattern has effected the saturation of the stroke and the effect of changing the Paper Brightness setting. The luminosity variations in the paper texture also effect the colors/values presented in the brush stroke.

     

     
    Finally, by selecting the Black pattern and setting the Paper Contrast to 0 percent, both pattern and paper texture are excluded from the resulting brush stroke.

    In this case, moving the Paper Brightness slider to the right shifts towards the selected main color, whilst moving it to the left shifts towards the additional color (value).

     

    SGC Variants in Grainy Mode

    As previously touched upon, the Soft Grain Colorize algorithm employs a cover method, so unlike say the default Square Chalk, there is no associated transparency corresponding to areas of white in a high contrast paper texture. Associated transparency can however be achieved by painting on a layer with the blending mode set to Gel or Multiply.

     
    Note that the Main Color in the Colors palette has been set to white, in order to achieve colorless transparency corresponding to the white areas of the paper texture.

    Because we are now in Gel blending mode, the color of the imagery on the Gel layer appears different over the underlying colored region on the Canvas. 

    In normal grainy mode, the resulting brush strokes can appear rather sterile and non-painterly. This is fine if you are looking for this effect (probably ideal for tone application), and although the SGC algorithm does not readily lend itself to yielding a painterly appearance in this mode, there are several things we can do to make the stroke visually more interesting.

     
    For this demonstration (above), the custom SGC Hard Basic Round variant has been selected, and brush opacity reduced to 9 percent. By making the additional color slightly darker than the main color, a subtle grain soak-in effect is achieved, giving an overall watercolor appearance.

    I imagine that in conjunction with one of the watercolor papers, the results could be quite pleasing.

     

     
    Here, the size of the SGC Ren Pen 2.5 variant has been increased in combination with a contrasting black and green for the main and additional colors respectively.

    Remember that as this is a rendered 'Ren' type variant, the custom Black pattern needs to be selected prior to making a brush stroke.

    When used with my custom 'P' paper texture, the lower blocked in area looks too uniform, whereas using the same texture and color combination in line art or text format with contrasting white space appears more interesting and appealing.

     

     
    In the Random section of the Brush Controls there is a check box to select the Random Brush Stroke Grain (RBSG) option. As the name suggests, the occurrence of paper texture in the brush stoke is randomized, resulting in a more organic appearance.

    Several variants, denoted by the letters RBSG in their name are included in the SGC brush library download. These have been saved with the Random Brush Stroke Grain option checked.

    The final demo image above shows the results of applying the normal SGC Hard Basic Round variant using the previous paper and color combination (far left), followed by the SGC Hard Basic RBSG variant (middle at default opacity and right at 100 percent opacity). Note that the Rendered 'Ren' variants do not support this feature.


    Resource Download


    The download comprises of the following;

    • a complete zipped brush library for Painter 7 and upwards. 

    There are no restrictions on use, other than the resources are not to be offered for sale or redistributed without my prior consent.


    Download SGC.zip (152 KB) for both PC and Mac platforms.

     

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