if n > len(p) {
		// Pad with black.
		clear(dst[3*len(p) : 3*n])
	}
	return 3 * n, nil
}

func (e *encoder) colorTablesMatch(localLen, transparentIndex int) bool {
	localSize := 3 * localLen
	if transparentIndex >= 0 {
		trOff := 3 * transparentIndex
		return bytes.Equal(e.globalColorTable[:trOff], e.localColorTable[:trOff]) &&
			bytes.Equal(e.globalColorTable[trOff+3:localSize], e.localColorTable[trOff+3:localSize])

	b := &bytes.Buffer{}
	b.WriteString(headerStr)
	b.WriteString(paletteStr)
	for transparentIndex := 0; transparentIndex < 3; transparentIndex++ {
		if transparentIndex < 2 {
			// Write the graphic control for the transparent index.
			b.WriteString("\x21\xf9\x04\x01\x00\x00")
			b.WriteByte(byte(transparentIndex))
			b.WriteByte(0)
		}
		// Write an image with bounds 2x1, as per TestDecode.

		if !useLocalColorTable {
			// Clone the global color table.
			m.Palette = append(color.Palette(nil), d.globalColorTable...)
		}
		if ti := int(d.transparentIndex); ti < len(m.Palette) {
			m.Palette[ti] = color.RGBA{}
		} else {
			// The transparentIndex is out of range, which is an error
			// according to the spec, but Firefox and Google Chrome
			// seem OK with this, so we enlarge the palette with