QOI.jl - Implementation of the QOI (Quite OK Image) format

This Julia package contains a decoder and encoder for the QOI image format. The QOI format is very simple and can be faster than using PNG (see the benchmarks) at the cost of a slightly worse compression ratio.

The code here is based on the reference C implementation given in https://github.com/phoboslab/qoi.

FileIO API

This is the simplest API and likely the one that most should use. Simply, use the load/save API from FileIO.jl to load and save QOI images.

using FileIO
image = load("test.qoi")
save("test2.qoi", image)

Basic API

• QOI.qoi_decode(f::Union{String, IO}) - Read an image in the QOI format from the file/IO f and return a matrix with RGB or RGBA colorants from ColorTypes.jl
• QOI.qoi_encode(f::Union{String, IO}, image::AbstractMatrix{<:Colorant}) - Write the image to the the file/IO f.

Advanced API

The QOI format is read in row-major order. This means that a transpose is required to create the matrices returned in the basic API. To avoid this, the following more advanced APIs exist:

• QOI.qoi_decode_raw(v::AbstractVector{UIt8}}) - Takes a vector of the bytes of an image in QOI format and returns the uncompressed vector of bytes from decoding.

• QOI.qoi_encode_raw(image::AbstractVecOrMat{UInt8}, header::QOI.QOIHeader) - Returns the bytes from compressing the bytes in image. The required header is defined as

  struct QOIHeader
    width::UInt32
    height::UInt32
    channels::QOI.QOIChannel # @enum
    colorspace::QOI.QOIColorSpace # @enum
  end

  where channels can be either QOI.QOI_RGB or QOI.QOI_RGBA and colorspace can be either QOI.QOI_SRGB or QOI.QOI_LINEAR

• QOI.qoi_encode_raw!(data::AbstractVecOrMat{UInt8}, image::AbstractVecOrMat{UInt8}, header::QOIHeader) - Same as above except writing the compressed data into data.

Benchmarks

The benchmarks here compares the speed of encoding/decoding images with QOI.jl and PNGFiles.jl (which uses libpng) It is supposed to mimic https://qoiformat.org/benchmark/. The images used in the benchmark are taken from TestImages.jl, specifically, all the PNG images in https://testimages.juliaimages.org/stable/imagelist/. The benchmarks were run on Linux on a 12th Gen Intel(R) Core(TM) i9-12900K CPU. They can be repeated by running the benchmark/runbenchmarks.jl file with the associated environment.

Expand to see benchmark results

autumn_leaves.png 105x140 57.42kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	0.24	0.41	233.52	137.4	22.18	38.6%
QOI	0.04	0.13	1418.35	425.17	28.25	49.2%

---

barbara_color.png 576x720 1215.0kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	9.05	14.07	131.12	84.35	812.84	66.9%
QOI	3.52	5.03	337.19	235.74	945.75	77.8%

---

chelsea.png 300x451 396.39kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	2.24	4.4	172.82	88.02	218.84	55.2%
QOI	0.64	1.55	605.92	250.3	233.27	58.8%

---

coffee.png 400x600 703.12kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	5.35	11.6	128.28	59.19	443.18	63.0%
QOI	1.98	5.23	346.76	131.24	493.3	70.2%

---

fabio_color_256.png 256x256 192.0kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	1.56	2.11	119.84	88.84	118.0	61.5%
QOI	0.54	0.86	344.22	216.96	154.86	80.7%

---

fabio_color_512.png 512x512 768.0kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	5.42	8.0	138.44	93.76	327.45	42.6%
QOI	2.04	3.13	366.9	239.9	463.9	60.4%

---

fabio_gray_256.png 256x256 192.0kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	1.08	1.65	174.16	113.7	108.65	56.6%
QOI	0.38	0.78	491.28	239.6	87.99	45.8%

---

fabio_gray_512.png 512x512 768.0kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	3.68	5.84	203.88	128.53	259.41	33.8%
QOI	1.55	2.99	483.08	251.05	298.29	38.8%

---

lena_gray_16bit.png 256x256 192.0kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	1.12	1.7	167.17	109.98	100.71	52.5%
QOI	0.4	0.78	468.04	241.2	82.01	42.7%

---

lighthouse.png 512x768 1152.0kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	8.4	13.02	133.94	86.39	692.56	60.1%
QOI	3.41	8.14	329.92	138.25	638.75	55.4%

---

monarch_color.png 512x768 1152.0kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	8.36	13.34	134.6	84.3	613.23	53.2%
QOI	3.64	5.04	309.24	223.43	715.79	62.1%

---

monarch_color_256.png 256x256 192.0kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	1.24	2.3	150.65	81.55	129.52	67.5%
QOI	0.34	1.46	557.65	128.6	144.39	75.2%

---

mountainstream.png 512x768 1152.0kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	8.8	13.46	127.78	83.6	892.34	77.5%
QOI	3.05	4.41	369.44	255.16	824.83	71.6%

---

toucan.png 150x162 94.92kB

	decode ms	encode ms	decode mpps	encode mpps	size kb	rate
PNGFiles	0.34	0.58	274.49	158.87	25.84	27.2%
QOI	0.06	0.18	1513.03	514.79	43.28	45.6%