View source for Layer

=== Layer ===

{{Template:FuncDef|Layer(clip ''base_clip'', clip ''overlay_clip'', string ''op'', int ''level'', int ''x'', int ''y'', int ''threshold'', bool ''use_chroma'')}}

This filter can overlay two clips of different sizes (but with the same color format) using different operation modes.
For pixel-wise transparency information the 4th color channel of [[RGB32]] (A- or alpha-channel) is used as a mask.

;base_clip
: the underlying clip which determines the size and all other video and audio properties of the result.
;overlay_clip
: the clip which is merged onto clip.
;op
: the performed merge operation, which can be: "add", "subtract", "lighten", "darken", "fast", "mul"
;level
:0-257, the strength of the performed operation
:* 0: the base_clip is returned unchanged
:* 257 (256 for YUY2): the maximal strength is used
;x,y
:offset position of the overlay_clip
;threshold
:only implemented for "lighten" and "darken"
;use_chroma
:use chroma of the '''overlay_clip''', default=true. When false only luma is used.

There are some differences in the behaviour and the allowed parameter depending on the color format and the operation and here are the details:

*There is no mask (alpha-channel) in YUY2, so the alpha-channel is assumed to be fully opaque everywhere.
*# in RGB32 the alpha-channel of the '''overlay_clip''' is multiplied with '''level''', so the resulting alpha = (alpha_mask * level + 1) / 256. This means for full strength of operation alpha has to be 255 and '''level''' has to be 257.

These operators behave equally for [[RGB32]] or [[YUY2]]:

''fast'': use_chroma must be TRUE, level and threshold is not used. The result is simply the average of base_clip and overlay_clip.

''add'': threshold is not used. The difference between '''base_clip''' and '''overlay_clip''' is multiplied with alpha and added to the '''base_clip'''.
 alpha=0   -> only base_clip visible,
 alpha=128 -> base_clip and overlay_clip equally blended,
 alpha=255 -> only overlay_clip visible.
Formula used :-
: RGB32 :: base += ((overlay-base)*(alpha*level+1)>>8)>>8
: YUY2  :: base += ((overlay-base)*level)>>8

''subtract'': the same as add, but the '''overlay_clip''' is inverted before.

These operators seem to work correctly only in YUY2:

''mul'': threshold is not used. The base_clip is colored as overlay_clip, so use_chroma should be TRUE.
 alpha=0 -> only base_clip visible.
 alpha=255 -> approx. the same Luminance as Base but with the colors of [[Overlay]].

''lighten'': '''use_chroma''' must be TRUE. Performs the same operation as ''add'', but only when the result is BRIGHTER than the base the new values is used. With a higher threshold the operation is more likely, so with <code>threshold=255</code> it's the same as "add", with <code>threshold=0</code> the base_clip is more likely passed unchanged, depending on the difference between base_clip and overlay_clip.

''darken'': the same as "lighten", but it is performed only when the result is DARKER than the base.

The audio and framerate/framecount are taken from the first clip. 

====Examples====

This can be used to combine two captures of different broadcasts for reducing noise. A discussion of this idea can be found {{doom9|28438}}. A sample script (of course you have to ensure that the frames of the two clips match exactly -- use [[DeleteFrame]] if necessary):

 clip1 = AviSource("F:\shakira-underneath_your_clothes.avi").ConvertToYUY2
 clip2 = AviSource("F:\shakira-underneath_your_clothes2.avi").ConvertToYUY2
 return Layer(clip1, clip2, "fast")

=== Mask ===

{{Template:FuncDef|Mask(clip ''clip'', mask_clip ''clip'')}}

Applies a defined alpha-mask to clip, for use with Layer, by converting mask_clip to greyscale and using that for the mask (the alpha-channel) of RGB32. In this channel "black" means completely transparent and "white" means completely opaque. For those of you who familiar with Photoshop masks, the concept is the same. In fact you can create a black and white photo in Photoshop, load it in your script and use it as a mask.

Here is an example; ss.jpg is derived from a snapshot from a video clip, which served as a guideline to create the mask just using Paint. We use Imagesource to load the image in the script and Mask to apply it.

 bg = AviSource("01gray.avi").ConvertToRGB32()    # here is the background clip
 mk = Imagesource("ss.jpg").ConvertToRGB32()      # load the image
 top = AviSource("k3.avi").ConvertToRGB32().Mask(mk) # load the top layer clip and apply the mask to it
 Layer(bg, top)                                   # layer the background and the top layer clip with the mask

=== ResetMask ===

{{Template:FuncDef|ResetMask(clip ''clip'')}}

Applies an "all-opaque" (that is white) alpha-mask to clip, for use with Layer. The alpha-channel of a RGB32-clip is not always well-defined (depending on the source), this filter is the faster way to apply an all white mask:

 clip = ResetMask(clip)


=== ColorKeyMask ===

{{Template:FuncDef|ColorKeyMask(clip ''clip'', int ''color'' [, int ''tolB'', int ''tolG'', int ''tolR''])}}

Clears pixels in the alpha-channel by comparing the color (default black). Each pixel with a color differing less than (''tolB'',''tolR'',''tolG'') (default 10) is set to transparent (that is black), otherwise it is left unchanged i.e. It is NOT set to opaque (that it is not set to white, that's why you might need [[ResetMask]] before applying this filter), this allows a aggregate mask to be constructed with multiple calls. When ''tolR'' or ''tolG'' are not set, they get the value of ''tolB'' (which reflects the old behaviour). Normally you start with a ResetMask, then chain a few calls to ColorKeyMask to cause transparent holes where each color of interest occurs. See [[Overlay]] for examples.

For AviSynth versions older than v2.58, there were no separate tolerance levels for blue, green and red. There was only one tolerance level called "tolerance" and this was used for blue, green and red simultaneously.

[[Category:Internal filters]]