Chroma transparency & frame disposal

GIF transparency in this API is indexed-color chroma transparency: the encoder selects one palette color as transparent for a frame. It is not per-pixel alpha in the encoded GIF.

#transparentColor

Global: GIFOptions.transparentColor
Per frame: GIFInputFrame.transparentColor / GIFEncodedFrame.transparentColor

Accepted forms:

• #RRGGBB
• RRGGBB
• 0xRRGGBB
• #RRGGBBAA / RRGGBBAA (the encoder uses the RGB portion)
• a 24-bit integer from 0x000000 through 0xFFFFFF
• null to explicitly disable chroma transparency

Invalid strings, negative numbers, non-integers, and numeric values above 0xFFFFFF are rejected before encoding.

##Precedence

For every frame:

1frame.transparentColor2  if defined3else options.transparentColor4  if defined5else no transparent color

Because null is distinct from undefined, a frame can explicitly turn off a global transparent color:

1await painter.createGIF(2  [3    { buffer: keyedFrame, transparentColor: '#00ff00' },4    { buffer: opaqueFrame, transparentColor: null },5  ],6  {7    outputFormat: 'buffer',8    width: 480,9    height: 270,10    transparentColor: '#ff00ff',11  }12);

#Disposal (GIFDisposalMethod)

Supported codes are:

Per-frame dispose overrides GIFOptions.defaultDispose.

When neither is supplied, Apexify resets the encoder disposal mode deterministically for each frame:

• 2 when no transparent color is active
• 0 when chroma transparency is active

This reset matters because encoder settings are stateful. A frame-local disposal/transparency override does not silently leak into later frames.

#Quantization caveat

The requested transparent RGB value is matched against the quantized GIF palette. Anti-aliased edges may contain neighboring colors and therefore remain partially visible. For chroma-key workflows, use hard edges or prepare the source frames accordingly.