alpha

alpha

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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gst-launch-1.0 videotestsrc pattern=snow ! mixer.sink_0 \
  videotestsrc pattern=smpte75 ! alpha method=green ! mixer.sink_1 \
  videomixer name=mixer sink_0::zorder=0 sink_1::zorder=1 ! \
  videoconvert ! autovideosink

This pipeline adds a alpha channel to the SMPTE color bars with green as the transparent color and overlays the output on top of 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

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