How to convert an image to ETC2 format? (KTX file)

With TexturePacker's --convert-texture command line option you can easily convert a single image to a different format:

TexturePacker --convert-texture input.png \
              --pixel-format ETC2 --texture-format ktx2

The pixel format specifies the compression algorithm to use, the texture format describes the file container. The following formats are supported for ETC:

Pixel format	Bits per pixel	Description
`ETC1_RGB`	4	ETC1 compression, no alpha channel
`ETC1_A`	4	ETC1 compression, alpha channel only
`ETC2_RGB`	4	ETC2 compression, no alpha
`ETC2_RGBA`	8	ETC2 compression, color+alpha

Texture Format	Description
`ktx`	Khronos Texture. Standard container for OpenGL ES textures.
`ktx2`	Khronos Texture (Version 2). Newer format with Basis Universal support.
`zktx`	Khronos Texture (gzip compressed). KTX file compressed for smaller storage.
`pkm`	ETC texture container. Simple format for ETC1/ETC2 compressed textures.
`pvr3`	PowerVR Texture Format. Native format for iOS and PowerVR GPUs.
`pvr3gz`	PowerVR Texture Format, compressed with gzip. Smaller on disk, decompressed at load time.
`pvr3ccz`	PowerVR Texture Format, compressed with zlib, cocos2d header.

The Image quality can be configured with --etc1-quality <0-100> and --etc2-quality <0-100>, default value is 70.
For other options (scaling, trimming transparency, ...) have a look at the Image conversion documentation.