► |  | Images

1 | Icons
2 | Logos
3 | Embedding Bitmaps in Compiled Files
4 | Floating-Point Bitmaps

▼ | 4 | Floating-Point Bitmaps

4.1 | Overview
4.2 | Struct Type and Accessors
4.3 | Conversion and Construction
4.4 | Component Operations
4.5 | Pointwise Operations
4.6 | Gradients and Normals
4.7 | Blur
4.8 | Resizing
4.9 | Compositing
4.10 | Spatial Transformations
4.11 | Effects

On this page:

flomap-pin
flomap-pin*
flomap-lt-superimpose
flomap-lc-superimpose
flomap-lb-superimpose
flomap-ct-superimpose
flomap-cc-superimpose
flomap-cb-superimpose
flomap-rt-superimpose
flomap-rc-superimpose
flomap-rb-superimpose
flomap-vl-append
flomap-vc-append
flomap-vr-append
flomap-ht-append
flomap-hc-append
flomap-hb-append

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#### 4.9`` Compositing

Unless stated otherwise, compositing functions assume every flomap argument has an alpha component.

> > procedure

> > ( flomap-pin fm1 x1 y1 fm2) → flomap

> fm1 : flomap
> x1 : Integer
> y1 : Integer
> fm2 : flomap
> ( flomap-pin fm1 x1 y1 fm2 x2 y2) → flomap
> fm1 : flomap
> x1 : Integer
> y1 : Integer
> fm2 : flomap
> x2 : Integer
> y2 : Integer

Superimposes fm2 over fm1 so that point x2 y2 on flomap f2 is directly over point x1 y1 on flomap f1. If x2 and y2 are not provided, they are assumed to be 0. The result is expanded as necessary.

fm1 and fm2 must have the same number of components.

Examples:

> > ( flomap-pin fm -10 -10 sine-fm)
> flomap-pin28: broke its contract
> promised a procedure that accepts 4 mandatory arguments and
> up to 2 optional arguments without any keywords
> produced: #<procedure:flomap-pin>
> in: (->*
> (flomap? Integer Integer flomap?)
> (Integer Integer)
> flomap?)
> contract from:
> <collects>/images/private/flomap-composite.rkt
> blaming:
> <collects>/images/private/flomap-composite.rkt

> > ( define circle-fm
> ( draw-flomap ( λ (fm-dc)
> ( send fm-dc set-pen "black" 4 'short-dash)
> ( send fm-dc set-brush "yellow" 'solid)
> ( send fm-dc set-alpha 1/2)
> ( send fm-dc draw-ellipse 2 2 124 124))
> 128 128))

> > ( flomap->bitmap ( flomap-pin fm 0 0 circle-fm 64 64))
> flomap-pin28: broke its contract
> promised a procedure that accepts 4 mandatory arguments and
> up to 2 optional arguments without any keywords
> produced: #<procedure:flomap-pin>
> in: (->*
> (flomap? Integer Integer flomap?)
> (Integer Integer)
> flomap?)
> contract from:
> <collects>/images/private/flomap-composite.rkt
> blaming:
> <collects>/images/private/flomap-composite.rkt
> > ( flomap->bitmap ( flomap-pin sine-fm 50 0 sine-fm))
> flomap-pin28: broke its contract
> promised a procedure that accepts 4 mandatory arguments and
> up to 2 optional arguments without any keywords
> produced: #<procedure:flomap-pin>
> in: (->*
> (flomap? Integer Integer flomap?)
> (Integer Integer)
> flomap?)
> contract from:
> <collects>/images/private/flomap-composite.rkt
> blaming:
> <collects>/images/private/flomap-composite.rkt

The other compositing functions are defined in terms of flomap-pin.

> > procedure

> > ( flomap-pin* |  | x1-frac |  |  |  |
> > |  | y1-frac |  |  |  |
> > |  | x2-frac |  |  |  |
> > |  | y2-frac |  |  |  |
> > |  | fm0 |  |  |  |
> > |  | fm ...) |  | → |  | flomap

> x1-frac : Real
> y1-frac : Real
> x2-frac : Real
> y2-frac : Real
> fm0 : flomap
> fm : flomap

For each adjacent pair fm1 fm2 in the argument list, pins fm2 over fm1.

The pin-over points are calculated from the four real arguments as follows. If fm1 is size w1×h1, then x1 = ( * w1 x1-frac) and y1 = ( * h1 y1-frac), and similarly for x2 and y2.

The following example pins the upper-left corner of each fm2 over a point near the upper-left corner of each fm1:

> > ( flomap->bitmap ( flomap-pin* 1/8 1/8 0 0
> circle-fm circle-fm circle-fm))

All the flomap superimpose and append functions are defined using flomap-pin* with different pin-over point fractions. For example, ( flomap-lt-superimpose fm0 fm ... ) = ( flomap-pin* 0 0 0 0 fm0 fm ... ), and ( flomap-vc-append fm0 fm ... ) = ( flomap-pin* 1/2 1 1/2 0 fm0 fm ... ).

> > procedure

> > ( flomap-lt-superimpose fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

> > procedure

> > ( flomap-lc-superimpose fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

> > procedure

> > ( flomap-lb-superimpose fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

> > procedure

> > ( flomap-ct-superimpose fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

> > procedure

> > ( flomap-cc-superimpose fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

> > procedure

> > ( flomap-cb-superimpose fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

> > procedure

> > ( flomap-rt-superimpose fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

> > procedure

> > ( flomap-rc-superimpose fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

> > procedure

> > ( flomap-rb-superimpose fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

These create a new flomap by superimposing the flomaps in the argument list. The two-letter abbreviation determines the pin-over points. For example, flomap-lt-superimpose (“flomap left-top superimpose”) pins points 0 0 together on each adjacent pair of flomaps:

> > ( flomap->bitmap ( flomap-lt-superimpose fm circle-fm))

See flomap-pin and flomap-pin* for implementation details.

> > procedure

> > ( flomap-vl-append fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

> > procedure

> > ( flomap-vc-append fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

> > procedure

> > ( flomap-vr-append fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

> > procedure

> > ( flomap-ht-append fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

> > procedure

> > ( flomap-hc-append fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

> > procedure

> > ( flomap-hb-append fm0 fm ...) → flomap

> fm0 : flomap
> fm : flomap

These create a new flomap by spatially appending the flomaps in the argument list. The two-letter abbreviation determines direction (v or h) and alignment (l, c, r, or t, c, b).

Example:

> > ( flomap->bitmap ( flomap-ht-append circle-fm fm
> ( flomap-scale circle-fm 1/2)))

See flomap-pin and flomap-pin* for implementation details.
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