Learn Phoduit

5.2 Masks

Masks are greyscale images used when blending to select which pixels in the source image are blended. White pixels in a mask indicate that the source image should be blended and black pixels indicate that the source image should not be blended. A mask’s grey values vary anywhere in between and are useful for making the effect appear smoother.

There are many different ways to create masks. The simplest is to use the Solid Color node but a solid colored mask affects the entire source image equally. You’ll usually use the Color Mask and the Paint Canvas nodes so you can target specific parts of your image.

Color Mask Node

The Color Mask node creates a greyscale image using colors in a specified range. Pixels from the input image with colors that are between the specified Minimum and Maximum ranges are white in the output image and colors outside that range are black. The ranges within the Minimum and Maximum fields define a greyscale ramp to soften the transition between tones.

Similar to the Blend node discussed in the last section, multiple images can be added to a Color Mask node to produce a single output image. This makes it easy to create masks that are based on a mix of images that are to be blended together.

Channel
The current channel visible for adjustment. All channels are used to produce the output image.
Minimum
The minimum range of non-black tones in the output image. Tones to the left of the range are black. Tones to the right of the range and left of the Maximum field’s range are white. Tones in between are interpolated as grey.
Maximum
The maximum range of non-black tones in the output image. Tones to the left of the range and right of the Minimum field’s range are white. Tones to the right of the range are black. Tones in between are interpolated as grey.

Paint Canvas Node

The Paint Canvas node is used for drawing pixels directly onto an image. It’s an easy way to set exactly which parts of an image should be blended without fiddling with tones. Because it can be used for creating new images, the Paint Canvas node is located under “Input” on the Nodes Toolbar. For the purpose of creating a mask, connect your source image to the “Image” input anchor and leave the Size field set to Match.

To paint, you must select the Paint Canvas node and then left click the Brush tool on the Tools Toolbar. Then just left click and move your mouse cursor around on the Canvas. If your mouse cursor looks like an X, the output of the selected Paint Canvas node is not visible to the Canvas. You can either connect it as normal or set the Canvas View combo box in the bottom right on the status bar to “Selected”.

You can change the color of your brush using the Color dock window on the right side. When painting masks, you usually want to stick to shades of grey. You can change grey intensities using the vertical lightness slider on the right side of the big hue circle.

The brush radius, opacity, and hardness can be adjusted using the Brush dock window above the Color dock window. The radius is how big the brush is. You’ll want to use a large brush first for large areas and then gradually reduce the radius to fill in detail. The opacity controls how strong each stroke is relative to the colors already painted. A very low opacity is useful for painting gradual tone. The hardness is the transition from opaque to transparent around the edge of the brush. A low hardness makes brush strokes appear fuzzy.

Painting masks by hand is not very hard but it can be time consuming. You should consider using it in conjunction with other methods to save time.

Further processing

Masks are images just like any photograph you’ve imported into Phoduit. This means they can use be processed using the same techniques you use to process your photographs. For example, you can use the Levels node to darken or brighten the greys which will change the intensity of the masked image when blending.

Another handy trick is to use the Blend node to merge masks together. This way you can build most of a mask with the Color Mask node and then do any quick touch up with the Paint Canvas node.

You’ll probably want to use the Addition, Multiply, and Subtract blend modes when blending masks.