UTEX.js

A fast, tiny tool for working with compressed textures (DDS etc.). It is used in Photopea.com. Try to open your compressed texture in Photopea to see how it works. It can compress and decompress following formats:

• Decompress: BC1, BC2, BC3, BC7 (a.k.a. DXT1, DXT3, DXT5, DX10) and ATC (ATI Texture Compression)
• Compress: BC1, BC3 (DXT1, DXT5)

The decompressed image (output of decompression, input to compression) is always "RGBA8".

Decoder

All functions have the same interface.

UTEX.readXYZ(data, offset, img, w, h)

• data: Uint8Array with a compressed file
• offset: where in "data" is the start of the image
• img: the output array (Uint8Array for RGBA8), which will be filled from the beginning
• w, h: the width and the height of an output image (usually a multiple of 4)

Actual functions are:

UTEX.readBC1(...)
UTEX.readBC2(...)
UTEX.readBC3(...)
UTEX.readBC7(...)
UTEX.readATC(...)

Encoder

All functions have the same interface.

UTEX.writeXYZ(img, w, h, data, offset)

• img: the input image (Uint8Array of RGBA8)
• w, h: the width and the height of the image (usually a multiple of 4)
• data: Uint8Array to write the data into
• offset: where in "data" should the image start

Actual functions are:

UTEX.writeBC1(...)
UTEX.writeBC3(...)

UTEX.DDS.js

This tool can parse entire DDS files (header + compressed texture). Inside, it calls the appropriate UTEX.readXYZ function according to the header.

UTEX.DDS.decode(buff)

• buff: ArrayBuffer containing the binary DDS file
• returns an array of images (mipmap levels, usually 1). An image is an object with:
• • width: the width of the image
• • height: the height of the image
• • image: ArrayBuffer with RGBA8 content

UTEX.DDS.encode(img, w, h)

• img: ArrayBuffer containing the RGBA image
• w, h: the width and the height of the image (usually a multiple of 4)
• returns an ArrayBuffer of the DDS file

This DDS encoder uses BC1 when all Alpha values are 255, and BC3 otherwise. It also creates all Mipmap levels.