#37 Masking an Image with a Vector Shape
Vector masking is one of Fireworks most powerful features. It is a nondestructive way of cropping a bitmap image, where both the bitmap and vector remain editable after the mask has been applied. Compared to bitmap masks, vector masks tend to have a higher degree of control and accuracy because you use a path, not a brush, to create them. It’s easy to change the fill or stroke of a vector mask. Generating the same type of effect with a bitmap mask can be more time consuming.
Vector masks use one of two modes: Path Outline or Grayscale Appearance. In Path Outline mode, the vector mask acts like a cookie cutter, using the shape of the path to act as the mask.
In Grayscale Appearance, any bitmap information in the vector’s fill gets converted to an alpha channel and fades the image accordingly. The Creative command Auto Vector Mask works in this way.
You will find both modes in the Property Inspector.
Whether you have drawn a vector shape using a tool from the Tools panel or have used the Pen tool to create your own custom shape, you can easily apply it as a mask to an existing bitmap or even another vector.
To mask a bitmap with a vector, draw the vector shape and position it over the top of the image. The image information outside the shape will be hidden when the mask is applied. You can apply the mask in a few ways.
Method 1 :
- Select both objects.
- Select Modify > Mask > Group as Mask.
This method automatically sets the mask to Grayscale Appearance mode, so if your vector was set to any color but white, you’ll notice that the image is semitransparent. To get a solid appearance, switch to Path Outline or select the mask in the Layers panel and change the Fill color to white.
- Select the vector only.
- Cut the vector shape (Ctrl/Command+X).
- Select the image.
- Select Edit > Paste as Mask.
This method automatically sets the mask to Path Outline regardless of the Fill color or style.
- Select the image.
- Cut the image from the canvas.
- Select the vector.
- Select Edit > Paste Inside.
The end result is identical to Method 2.
Once the image is masked you will see an image and a mask thumbnail in the Layers panel (Figure 37a).
Figure 37a A bitmap image masked by a vector shape.
On the canvas you can reposition the image within the mask by using the Pointer tool and dragging the small blue fleur in the center of the image. You can also break the link between the image and the mask by clicking the chain link icon in the Layers panel.
By selecting Show Fill and Stroke, you can experiment with a variety of custom edges with the Stroke options, even by just choosing some of the more abstract Stroke categories such as Oil, Random, or (my personal favorite) Unnatural. The possibilities are endless, so give some of the options a try. Figures 37b, 37c, 37d, and 37e show a few creative examples.
Figure 37b Soft stroke creates a border around the masked image.
Figure 37c Changing the Stroke type (Stroke > Unnatural > Viscous Alien Paint) results in a completely different look.
Figure 37d The Outline Stroke type creates an interesting framing effect.
Figure 37e The anchor points of the vector mask can still be edited using the Subselection or Pen tool, giving you many creative options.