ktx-parse

What is ktx-parse?

The ktx-parse npm package is a utility for parsing KTX (Khronos Texture) files, which are used for storing textures in a standardized format. This package allows developers to read and manipulate KTX files in JavaScript, making it useful for applications that need to handle texture data, such as game engines, 3D rendering applications, and other graphics-related software.

What are ktx-parse's main functionalities?

Parsing KTX Files

This feature allows you to parse a KTX file and extract its contents. The code sample demonstrates how to read a KTX file from the filesystem and parse it using the ktx-parse package.

const ktxParse = require('ktx-parse');
const fs = require('fs');

const ktxData = fs.readFileSync('path/to/texture.ktx');
const parsedKTX = ktxParse(ktxData);
console.log(parsedKTX);

Accessing Texture Data

This feature allows you to access the raw texture data from a parsed KTX file. The code sample shows how to extract the texture data from the first mip level of the parsed KTX file.

const ktxParse = require('ktx-parse');
const fs = require('fs');

const ktxData = fs.readFileSync('path/to/texture.ktx');
const parsedKTX = ktxParse(ktxData);
const textureData = parsedKTX.levels[0].levelData;
console.log(textureData);

Extracting Metadata

This feature allows you to extract metadata from a KTX file. The code sample demonstrates how to read the key-value metadata pairs from a parsed KTX file.

const ktxParse = require('ktx-parse');
const fs = require('fs');

const ktxData = fs.readFileSync('path/to/texture.ktx');
const parsedKTX = ktxParse(ktxData);
const metadata = parsedKTX.keyValue;
console.log(metadata);

Other packages similar to ktx-parse

ktx

The ktx package is another utility for working with KTX files. It provides similar functionality to ktx-parse, including parsing and manipulating KTX files. However, ktx-parse is often preferred for its simplicity and ease of use.

three

The three package is a popular 3D library that includes support for loading and using KTX textures. While it offers a broader range of features for 3D rendering, it may be more complex to use if you only need to work with KTX files.

gl-texture2d

The gl-texture2d package is a WebGL utility for handling 2D textures, including KTX files. It provides functionality for creating and managing textures in WebGL, making it a good choice for web-based graphics applications.

README

ktx-parse

KTX 2.0 (.ktx2) parser and serializer.

Quickstart

Install:

npm install --save ktx-parse

Import:

// ES Modules:
import { read, write } from 'ktx-parse';

// CommonJS:
const { read, write } = require('ktx-parse');

Usage:

// Parse texture container from file:
const texture = read(data /* ← Uint8Array or Buffer */);

// Write texture container to file:
const data = write(texture); // → Uint8Array

See API documentation for more details.

Encoding / Decoding

KTX-Parse reads/writes KTX 2.0 containers, and provides access to the compressed texture data within the container. To decompress that texture data, or to compress existing texture data into GPU texture formats used by KTX 2.0, you'll need to use additional libraries such as encoders or transcoders.

Encoding:

Encoding GPU textures is a slow process, and should be completed at development/authoring time so that the compressed texture can be transmitted to the viewing device. GPU textures require much less GPU memory than image formats like PNG or JPEG, and can be uploaded to the GPU quickly with less impact on framerate. GPU textures can also have smaller filesizes in many, but not all, cases. See the Basis documentation for details on this process.

• BinomialLLC/basis_universal provides C++ and WebAssembly encoders, reading PNG files or raw pixel data, and outputing compressed texture data (and supercompression global data, if applicable). Use of these encoders is somewhat advanced, and the simpler basisu CLI tool does not provide the data necessary for writing a KTX 2.0 file.
• KhronosGroup/KTX-Software provides CLI, C++, and WebAssembly encoders for reading PNG or JPEG textures and outputing a complete KTX 2.0 file, which ktx-parse can then read or edit. While probably easier than using the basis_universal encoders directly, the KTX-Software library is somewhat larger and has more dependencies.

Transcoding / Decoding:

Basis Universal texture formats (ETC1S and UASTC) cannot be directly read by a GPU, but are designed to be very efficiently rewritten into many of the specific GPU texture formats that different GPUs require. This process is called transcoding, and typically happens on the viewing device after a target output format (e.g. ETC1, ASTC, BC1, ...) is chosen. These transcoders can also fully decode texture data to uncompressed RGBA formats, if raw pixel data is required.

• BinomialLLC/basis_universal provides official C++ and WebAssembly transcoders, which support all Basis Universal input formats and can transcode to any output format (with appropriate compilation flags). With common settings, a transcoder will likely be > 200kb on web.
• KhronosGroup/Universal-Texture-Transcoders provides very small, fast WebAssembly transcoders each supporting only a single output texture format. Each transcoder is roughly 10-20kb, and the viewing device can choose which transcoder to download, as appropriate. Only UASTC texture formats currently supported.

The transcoders above cannot read KTX 2.0 files directly. Instead, unpack the KTX 2.0 files with ktx-parse first, then transcode the mip levels using a low-level transcoder.

API Documentation

Functions

read

▸ read(data: Uint8Array): KTX2Container

Defined in src/read.ts:14

Parses a KTX 2.0 file, returning an unpacked KTX2Container instance with all associated data. The container's mip levels and other binary data are pointers into the original file, not copies, so the original file should not be overwritten after reading.

Parameters:

Name	Type	Description
data	Uint8Array	Bytes of KTX 2.0 file, as Uint8Array or Buffer.

Returns: KTX2Container

write

▸ write(container: KTX2Container, options?: WriteOptions): Uint8Array

Defined in src/write.ts:21

Serializes a KTX2Container instance to a KTX 2.0 file. Mip levels and other binary data are copied into the resulting Uint8Array, so the original container can safely be edited or destroyed after it is serialized.

Options:

• keepWriter: If true, 'KTXWriter' key/value field is written as provided by the container. Otherwise, a string for the current ktx-parse version is generated. Default: false.

Parameters:

Name	Type	Default value	Description
container	KTX2Container	-
options	WriteOptions	{}

Returns: Uint8Array

Class: KTX2Container

Represents an unpacked KTX 2.0 texture container. Data for individual mip levels are stored in the .levels array, typically compressed in Basis Universal formats. Additional properties provide metadata required to process, transcode, and upload these textures.

Properties

dataFormatDescriptor

• dataFormatDescriptor: KTX2DataFormatDescriptorBasicFormat[] = [{ vendorId: KHR_DF_VENDORID_KHRONOS, descriptorType: KHR_DF_KHR_DESCRIPTORTYPE_BASICFORMAT, descriptorBlockSize: 0, versionNumber: KHR_DF_VERSION, colorModel: KHR_DF_MODEL_UNSPECIFIED, colorPrimaries: KHR_DF_PRIMARIES_BT709, transferFunction: KHR_DF_TRANSFER_SRGB, flags: KHR_DF_FLAG_ALPHA_STRAIGHT, texelBlockDimension: [0, 0, 0, 0], bytesPlane: [0, 0, 0, 0, 0, 0, 0, 0], samples: [], }]

Defined in src/container.ts:47

Data Format Descriptor.

---

faceCount

• faceCount: number = 1

Defined in src/container.ts:38

Number of cubemap faces. For cubemaps and cubemap arrays, faceCount must be 6. For all other textures, faceCount must be 1. Cubemap faces are stored in +X, -X, +Y, -Y, +Z, -Z order.

---

globalData

• globalData: KTX2GlobalDataBasisLZ | null = null

Defined in src/container.ts:65

Supercompression Global Data.

---

keyValue

• keyValue: { [key:string]: string | Uint8Array; }

Defined in src/container.ts:62

Key/Value Data.

---

layerCount

• layerCount: number = 0

Defined in src/container.ts:31

Number of array elements (array textures only).

---

levels

• levels: KTX2Level[] = []

Defined in src/container.ts:44

Mip levels, ordered largest (original) to smallest (~1px).

---

pixelDepth

• pixelDepth: number = 0

Defined in src/container.ts:28

Depth of the texture image for level 0, in pixels (3D textures only).

---

pixelHeight

• pixelHeight: number = 0

Defined in src/container.ts:25

Height of the texture image for level 0, in pixels.

---

pixelWidth

• pixelWidth: number = 0

Defined in src/container.ts:22

Width of the texture image for level 0, in pixels.

---

supercompressionScheme

• supercompressionScheme: number = KHR_SUPERCOMPRESSION_NONE

Defined in src/container.ts:41

Indicates which supercompression scheme has been applied to mip level images, if any.

---

typeSize

• typeSize: number = 1

Defined in src/container.ts:19

Size of the data type in bytes used to upload the data to a graphics API. When vkFormat is VK_FORMAT_UNDEFINED, typeSize must be 1.

---

vkFormat

• vkFormat: number = VK_FORMAT_UNDEFINED

Defined in src/container.ts:13

Specifies the image format using Vulkan VkFormat enum values. When using Basis Universal texture formats, vkFormat must be VK_FORMAT_UNDEFINED.