Overlaying Capabilities

Guide to Overlaying Capabilities.

Update for Snowmix version 0.4.5.

This is a guide to overlaying capabilities of feeds, virtual feeds, placed shapes, placed images and placed texts in Snowmix.

Snowmix can overlay/mix components such as feeds, virtual feeds, images, shapes and text using 2 different methods. These are stacking and overlay. The stacking method only applies to feeds. All other elements must be overlayed using commands executed as part of the command macro set with the command overlay finish.

The table below list the overlaying capabilities for feeds, virtual feeds, shapes, images and texts.

Capability	Feed	Virtual Feed	Shape Based Feed/Image	Image	Text
Stacking	yes	no	no	no	no
Overlay command	yes	yes	yes	yes	yes
Setting Coordinates	yes	yes	yes	yes	yes
Setting Alpha	yes	yes	yes	yes	yes
Setting Rotation	no	yes	yes	yes	yes
Automatic Animation	no	yes	yes	yes	yes
Rectangle Clipping	yes	yes	no, shape clip	yes	yes
Free Clipping	no	no	yes	no	no
PAR Pixel Aspect Ratio	yes	no, free scale	no, free scale	no, free scale	no
X-Y Linked Scaling	yes	no, free scale	no, free scale	no, free scale	no, free scale
Free X-Y Scaling	no	yes	yes	yes	yes
Matrix transformation	no	yes	yes	yes	no
Offset for rotation	no	yes	yes	yes	missing
Anchoring	no	yes	yes	yes	yes
Alignment	no	yes	yes	yes	yes
Overlay method - filter	yes	yes	yes	yes	no
Source Change	no	yes	yes	yes	yes
Overlay finish	optional	required	required	required	required
Gradient pattern blend	no	no	yes	no	no

Stacking: Only feeds can use the command stack for overlaying video. All other overlaying of elements must be set through the command macro set for the command overlay finish.

Overlay command: The overlay command must be executed as part of the command macro set with the command overlay finish. Commands: feed overlay fast, vfeed overlay, shape overlay, image overlay, text overlay

Setting Coordinates: Setting/changing the coordinates of placement. Commands: feed shift, vfeed coor, shape place coor, image coor, text coor

Setting Alpha: Setting/Changing the alpha value for overlay. Commands: feed alpha, vfeed alpha, shape place alpha, image alpha, text alpha

Setting Rotation: Setting/changing the rotation for overlay. Commands: vfeed rotation, shape place rotation, image rotation, text rotation.

Automatic Animation: Specifying linear automatic animation of parameters for coordinates, alpha, rotation, clipping and offset. Commands: vfeed move ..., shape place move ..., image move ..., text move ...

Rectangle Clipping: Clipping of source using a rectangle. Shape based clips do not have a command for rectangle clipping, but rectangle clipping and any other type of clipping can be defined as part of the shape the shape place command uses. Commands: feed cutout, vfeed clip, image clip, text clip.

Free Clipping: Free or arbitrary shape clipping of source. Placed shapes do not have a command for clipping, but any type of clipping can be defined as part of the shape the placed shape uses. Commands: shape clip and others.

PAR Pixel Aspect Ratio: Feeds are when overlayed, scaled according to pixel aspect ratio and its scale setting.. Virtual feeds, shape based feeds and images can use free X-Y scaling emulating Pixel Aspect Ratio or PAR. Commands: feed par, vfeed scale, shape place scale, image scale, text scale.

X-Y Linked Scaling: Scaling X and Y are linked together. Feeds only has one scaling value for both X and Y. The value is expressed as a fraction. Setting X scaling equal to Y-scaling simulates X-Y Linked Scaling for virtual feeds, shape placed feeds, images and texts. Commands: feed scale, vfeed scale, shape place scale, image scale, text scale.

Free X-Y Scaling: Scaling X and Y independently. Feeds only have one value fraction for scale used for both X and Y. However used in addition with the command feed par, independent X-Y scaling can be simulated. Commands: feed scale, feed par, vfeed scale, shape place scale, image scale, text scale.

Matrix Transformation: Overlay can be controlled through a Cairo Matrix Transformation providing many effects including mirroring. Commands: vfeed matrix, shape place matrix, image matrix.

Offset for rotation: Setting/changing offset affecting rotation by setting a rotation offset coordinate. Commands: vfeed offset, shape place offset, image offset, text offset.

Anchoring: Setting/changing coordinates relative to n, s, e, w, c, ne, nw, se, sw. Commands: vfeed anchor, shape place anchor, image anchor, text anchor

Alingment: Aligning overlay relative to coordinate using left, center, right, top, middle or bottom. Commands: vfeed align, shape place align, image align, text align.

Overlay method - filter: Setting Cairo filter method for overlaying. Options are fast, good, best, nearest, bilinear, gaussian. WARNING. This can heavily affects the load on the system when selecting a filter method different from fast. Placed shapes does not have a command for setting the filter, but the shape used by the placed shape can define an equivalent filter. Commands: feed filter, vfeed filter, shape filter, image filter.

Source Changing: Changing the source on the fly. vfeed source, shape place shape, image source, text string.

Overlay Finish: If set to yes, overlaying must take place as part of the command macro set with the command overlay finish executing the commands feed fast overlay, vfeed overlay, shape place overlay, image overlay and text overlay. Feeds will normally be overlayed using the command stack, but can optionally use the command feed fast overlay. Commands: overlay finish.

Gradient pattern blend: If yes, alpha blending and effectively also clipping can be set using gradient patterns. Commands: shape pattern ..., shape source pattern, shape paint.

Copyright Peter Maersk-Moller (c) 2012-2015. All rights reserved.