Spray

Creates a spray-paint effect. Click the left mouse button at the center of the region to be sprayed. The area covered is determined by the ``spray factor'' in the ``configuration'' menu. NOTE: Be sure to click the main ``Cancel'' button at left when finished to return to normal mode.

Fine spray

Creates a solid spray painting effect. Click the left mouse button at the center of the region to be sprayed. The area covered is determined by the ``spray factor'' in the ``configuration'' menu.

Diffuse spray

Diffuse spray sets the pixels around the cursor to the foreground (drawing) color, but in a diffuse pattern.

Math spray

Math spray allows you to enter any mathematical formula to be applied to all the pixels in a fixed area around the cursor. This can be used to interactively copy small parts of another image or a different part of the image. For example, you could enter the formula

i=image[1][0][x+100][y+100]; .

This would copy pixels from image no. 1, frame 0, 100 pixels to the right and below the mouse cursor, for a pattern retouching or texture mapping effect. The image number can be the same image or a different one (see image algebra ).

If the image is color, the red, green, and blue components can have independent equations.

If the image is wavelet-transformed, the wavelet components can be sprayed with equations such as

w*=10; .

Note: Because rebuilding the screen display is a relatively slow process, screen rebuilding is not done if the image depth differs from the screen depth until the mouse is released. This can cause colors to temporarily appear incorrect.

Filter spray

Filter spray applies the selected convolution filter to the pixels in a fixed area around the cursor. This can be used to interactively remove noise or blur small parts of the image. The spray area must be larger than the filter kernel size.

`Amount of Filtering' should be set to some small value (e.g. 1-2%) to avoid sharp discontinuities around the edge of the spray-filtered region.

Erase Spray

Restores area under the mouse cursor to its original state. This has the same effect as clicking the ``Erase'' button (see Sec. 14.1).

Line Spray

Extends the pixels using a user-selected line as a template, creating a drawing.

1. Select "Spray...Line pattern Spray"
2. Click "Accept"
3. Define the linear region to use as the template by click-and-dragging. If you click the mouse without dragging, the previous template, if any, will be used.
4. Move to the desired area to change and click and drag to draw. Pixels from the template will be copied to the new location. The pixels will be rotated in the direction of drawing to create a wide line.
5. If you release the mouse button and continue drawing somewhere else, the previous angle is remembered. This can cause undesirable artifacts in the drawing. If you want the new drawings to start at a different angle, click the main "cancel" button, and click "Accept" to start again and click without dragging to continue using the previous template.
6. Click the main cancel button in the information window when finished.