alpha

alpha — Adds an alpha channel to video - uniform or via chroma-keying

Properties

gdouble alpha Read / Write
gfloat angle Read / Write
GstAlphaMethod method Read / Write
gfloat noise-level Read / Write
guint target-b Read / Write
guint target-g Read / Write
guint target-r Read / Write
guint black-sensitivity Read / Write
guint white-sensitivity Read / Write
gboolean prefer-passthrough Read / Write

Types and Values

struct GstAlpha
enum GstAlphaMethod

Object Hierarchy

    GObject
    ╰── GInitiallyUnowned
        ╰── GstObject
            ╰── GstElement
                ╰── GstBaseTransform
                    ╰── GstVideoFilter
                        ╰── GstAlpha

Description

The alpha element adds an alpha channel to a video stream. The values of the alpha channel can be either be set to a constant or can be dynamically calculated via chroma keying, e.g. blue can be set as the transparent color.

Sample pipeline:

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2
3
gst-launch-1.0 videotestsrc pattern=smpte75 ! alpha method=green ! \
  videomixer name=mixer ! videoconvert ! autovideosink     \
  videotestsrc pattern=snow ! mixer.

with green as the transparent color and mixes the output with a snow video stream.

Synopsis

Element Information

plugin

alpha

author

Wim Taymans <wim.taymans@gmail.com> Edward Hervey <edward.hervey@collabora.co.uk> Jan Schmidt <thaytan@noraisin.net>

class

Filter/Effect/Video

Element Pads

name

sink

direction

sink

presence

always

details

video/x-raw, format=(string){ AYUV, ARGB, BGRA, ABGR, RGBA, Y444, xRGB, BGRx, xBGR, RGBx, RGB, BGR, Y42B, YUY2, YVYU, UYVY, I420, YV12, Y41B }, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ]

name

src

direction

source

presence

always

details

video/x-raw, format=(string){ AYUV, ARGB, BGRA, ABGR, RGBA, Y444, xRGB, BGRx, xBGR, RGBx, RGB, BGR, Y42B, YUY2, YVYU, UYVY, I420, YV12, Y41B }, width=(int)[ 1, 2147483647 ], height=(int)[ 1, 2147483647 ], framerate=(fraction)[ 0/1, 2147483647/1 ]

Functions

Types and Values

struct GstAlpha

struct GstAlpha;


enum GstAlphaMethod

Members

ALPHA_METHOD_SET

Set/adjust alpha channel

 

ALPHA_METHOD_GREEN

Chroma Key green

 

ALPHA_METHOD_BLUE

Chroma Key blue

 

ALPHA_METHOD_CUSTOM

Chroma Key on target_r/g/b

 

Property Details

The “alpha” property

  “alpha”                    gdouble

The value for the alpha channel.

Flags: Read / Write

Allowed values: [0,1]

Default value: 1


The “angle” property

  “angle”                    gfloat

Size of the colorcube to change.

Flags: Read / Write

Allowed values: [0,90]

Default value: 20


The “method” property

  “method”                   GstAlphaMethod

How the alpha channels should be created.

Flags: Read / Write

Default value: Set/adjust alpha channel


The “noise-level” property

  “noise-level”              gfloat

Size of noise radius.

Flags: Read / Write

Allowed values: [0,64]

Default value: 2


The “target-b” property

  “target-b”                 guint

The blue color value for custom RGB chroma keying.

Flags: Read / Write

Allowed values: <= 255

Default value: 0


The “target-g” property

  “target-g”                 guint

The green color value for custom RGB chroma keying.

Flags: Read / Write

Allowed values: <= 255

Default value: 255


The “target-r” property

  “target-r”                 guint

The red color value for custom RGB chroma keying.

Flags: Read / Write

Allowed values: <= 255

Default value: 0


The “black-sensitivity” property

  “black-sensitivity”        guint

Sensitivity to dark colors.

Flags: Read / Write

Allowed values: <= 128

Default value: 100


The “white-sensitivity” property

  “white-sensitivity”        guint

Sensitivity to bright colors.

Flags: Read / Write

Allowed values: <= 128

Default value: 100


The “prefer-passthrough” property

  “prefer-passthrough”       gboolean

Don't do any processing for alpha=1.0 if possible.

Flags: Read / Write

Default value: FALSE