**Shift Lens App 2.5**Help

# Curves, Anchor and Control points

The first step is to load a photo by choosing the menu File Open. After loading the photo, adding curve(s) is allowed. Whatever toolbox is chosen except "Ratio Adjustment", to add a curve press the "+" button and click where You want on the image.

Buttons for adding and removing curves:

Select the Curve Segments list and choose a number between 1 and 50.

If the "Vertical Straighten" tool is chosen, a vertical curve appears with a chosen number of curve segments. The same will be done with "Horizontal Straighten' tool.
To add another curve and so on, first press the "+" button and click where You want on the image. Adding curves are allowed in toolboxes Vertical and Horizontal Straighten. Every single curve can contain a different number of curve Segments.

If the "Angle Straighten" tool is chosen, a horizontal curve appears with 2 anchor points. Only one curve is allowed.

When the Advanced Horizontal or Advanced Vertical tool is chosen, border curves, Guide curve and Leading curve are drawn with one curve segment. After that, the user can change a number of curve segments on the selected curve.

If more than one curve is present, click on the one of anchor or control points on that curve to select it:

The selected curve has bigger anchor (quads) and control (circle) points - like the first curve from the right in the image above. The first and last Anchor points on a vertical curve can be moved only left or right. Inner points can be moved up, down, left and right. See the yellow arrows on the image below:

The first and last Anchor points on a horizontal curve can be moved only up or down. Inner points can be moved up, down, left and right - see yellow arrows in the image above.

To remove some curve, first select it by clicking on one of the points and press the "-" button. When one of the points is moved, the curve changes shape in real time.

In Vertical and Horizontal Straighten, the user can add as many curves as he wants - the number is unlimited. The number of Curve Segments is limited to 50. Every Curve Segment contains 4 points.

In Advanced Vertical and Horizontal Straighten, these things are different. There are only 2 Border curves and pairs that contain Guide and Leading curves. In Advanced Vertical Straighten, every new set of Guide and Leading curves will be positioned to the left side against the previous curves set. In Advanced Horizontal Straighten, every new curves set will be positioned above the previous curves set. The number of curves sets is limited because the new curves set cannot overlap the Upper Border curve in the Advanced Horizontal Straighten nor cannot overlap the Left Border curve in the Advanced Vertical Straighten.

Another important thing in Advanced Vertical and Horizontal Straighten is that the Guide curve and Leading curve cannot overlap border curves. Also, if there is more than one Guide and Leading Curves set, neither the Guide curve nor the Leading curve cannot overlap the Guide curve or Leading curve in another set. This rule is explained in detail in the next section "Scope of work area"