305 lines
11 KiB
C
305 lines
11 KiB
C
/* ************************************************************************** */
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/* */
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/* ::: :::::::: */
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/* qoi.h :+: :+: :+: */
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/* +:+ +:+ +:+ */
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/* By: maiboyer <maiboyer@student.42.fr> +#+ +:+ +#+ */
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/* +#+#+#+#+#+ +#+ */
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/* Created: 2023/12/24 17:39:36 by maiboyer #+# #+# */
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/* Updated: 2023/12/25 18:35:05 by maiboyer ### ########.fr */
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/* */
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/* ************************************************************************** */
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/*
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Copyright (c) 2021, Dominic Szablewski - https://phoboslab.org
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SPDX-License-Identifier: MIT
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QOI - The "Quite OK Image" format for fast, lossless image compression
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-- About
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QOI encodes and decodes images in a lossless format. Compared to stb_image and
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stb_image_write QOI offers 20x-50x faster encoding, 3x-4x faster decoding and
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20% better compression.
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-- Synopsis
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// Define `QOI_IMPLEMENTATION` in *one* C/C++ file before including this
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// library to create the implementation.
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#define QOI_IMPLEMENTATION
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#include "qoi.h"
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// Encode and store an RGBA buffer to the file system. The t_qoi_desc describes
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// the input pixel data.
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qoi_write("image_new.qoi", rgba_pixels, &(t_qoi_desc){
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.width = 1920,
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.height = 1080,
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.channels = 4,
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.colorspace = QOI_SRGB
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});
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// Load and decode a QOI image from the file system t_i32o a 32bbp RGBA buffer.
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// The t_qoi_desc struct will be filled with the width, height,
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number of channels
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// and colorspace read from the file header.
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t_qoi_desc desc;
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void *rgba_pixels = qoi_read("image.qoi", &desc, 4);
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-- Documentation
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This library provides the following functions;
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- qoi_read -- read and decode a QOI file
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- qoi_decode -- decode the raw bytes of a QOI image from memory
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- qoi_write -- encode and write a QOI file
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- qoi_encode -- encode an rgba buffer t_i32o a QOI image in memory
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See the function declaration below for the signature and more information.
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If you don't want/need the qoi_read and qoi_write functions, you can define
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QOI_NO_STDIO before including this library.
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This library uses malloc() and mem_free(). To supply your own malloc implementation
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you can define QOI_MALLOC and QOI_FREE before including this library.
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This library uses memset() to zero-initialize the index. To supply your own
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implementation you can define QOI_ZEROARR before including this library.
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-- Data Format
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A QOI file has a 14 byte header, followed by any number of data "chunks" and an
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8-byte end marker.
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struct qoi_header_t {
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char magic[4]; // magic bytes "qoif"
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ut_i3232_t width; // image width in pixels (BE)
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ut_i3232_t height; // sprite.height in pixels (BE)
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ut_i328_t channels; // 3 = RGB, 4 = RGBA
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ut_i328_t colorspace; // 0 = sRGB with linear alpha, 1 = all channels
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linear
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};
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Images are encoded row by row, left to right, top to bottom. The decoder and
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encoder start with {r: 0, g: 0, b: 0, a: 255} as the previous pixel value. An
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image is complete when all pixels specified by width * height have been covered.
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Pixels are encoded as
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- a run of the previous pixel
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- an index t_i32o an array of previously seen pixels
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- a difference to the previous pixel value in r,g,b
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- full r,g,b or r,g,b,a values
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The color channels are assumed to not be premultiplied with the alpha channel
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("un-premultiplied alpha").
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A running array[64] (zero-initialized) of previously seen pixel values is
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mat_i32ained by the encoder and decoder. Each pixel that is seen by the encoder
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and decoder is put t_i32o this array at the position formed by a hash function
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of the color value. In the encoder, if the pixel value at the index matches the
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current pixel, this index position is written to the stream as QOI_OP_INDEX.
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The hash function for the index is:
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index_position = (r * 3 + g * 5 + b * 7 + a * 11) % 64
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Each chunk starts with a 2- or 8-bit tag, followed by a number of data bits. The
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bit length of chunks is divisible by 8 - i.e. all chunks are byte aligned. All
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values encoded in these data bits have the most significant bit on the left.
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The 8-bit tags have precedence over the 2-bit tags. A decoder must check for the
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presence of an 8-bit tag first.
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The byte stream's end is marked with 7 0x00 bytes followed a single 0x01 byte.
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The possible chunks are:
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.- QOI_OP_INDEX ----------.
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| Byte[0] |
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| 7 6 5 4 3 2 1 0 |
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|-------+-----------------|
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| 0 0 | index |
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`-------------------------`
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2-bit tag b00
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6-bit index t_i32o the color index array: 0..63
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A valid encoder must not issue 2 or more consecutive QOI_OP_INDEX chunks to the
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same index. QOI_OP_RUN should be used instead.
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.- QOI_OP_DIFF -----------.
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| Byte[0] |
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| 7 6 5 4 3 2 1 0 |
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|-------+-----+-----+-----|
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| 0 1 | dr | dg | db |
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`-------------------------`
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2-bit tag b01
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2-bit red channel difference from the previous pixel between -2..1
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2-bit green channel difference from the previous pixel between -2..1
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2-bit blue channel difference from the previous pixel between -2..1
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The difference to the current channel values are using a wraparound operation,
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so "1 - 2" will result in 255, while "255 + 1" will result in 0.
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Values are stored as unsigned t_i32egers with a bias of 2. E.g. -2 is stored as
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0 (b00). 1 is stored as 3 (b11).
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The alpha value remains unchanged from the previous pixel.
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.- QOI_OP_LUMA -------------------------------------.
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| Byte[0] | Byte[1] |
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| 7 6 5 4 3 2 1 0 | 7 6 5 4 3 2 1 0 |
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|-------+-----------------+-------------+-----------|
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| 1 0 | green diff | dr - dg | db - dg |
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`---------------------------------------------------`
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2-bit tag b10
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6-bit green channel difference from the previous pixel -32..31
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4-bit red channel difference minus green channel difference -8..7
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4-bit blue channel difference minus green channel difference -8..7
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The green channel is used to indicate the general direction of change and is
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encoded in 6 bits. The red and blue channels (dr and db) base their diffs off
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of the green channel difference and are encoded in 4 bits. I.e.:
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dr_dg = (cur_px.r - prev_px.r) - (cur_px.g - prev_px.g)
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db_dg = (cur_px.b - prev_px.b) - (cur_px.g - prev_px.g)
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The difference to the current channel values are using a wraparound operation,
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so "10 - 13" will result in 253, while "250 + 7" will result in 1.
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Values are stored as unsigned t_i32egers with a bias of 32 for the green channel
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and a bias of 8 for the red and blue channel.
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The alpha value remains unchanged from the previous pixel.
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.- QOI_OP_RUN ------------.
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| Byte[0] |
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| 7 6 5 4 3 2 1 0 |
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|-------+-----------------|
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| 1 1 | run |
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`-------------------------`
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2-bit tag b11
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6-bit run-length repeating the previous pixel: 1..62
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The run-length is stored with a bias of -1. Note that the run-lengths 63 and 64
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(b111110 and b111111) are illegal as they are occupied by the QOI_OP_RGB and
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QOI_OP_RGBA tags.
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.- QOI_OP_RGB ------------------------------------------.
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| Byte[0] | Byte[1] | Byte[2] | Byte[3] |
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| 7 6 5 4 3 2 1 0 | 7 .. 0 | 7 .. 0 | 7 .. 0 |
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|-------------------------+---------+---------+---------|
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| 1 1 1 1 1 1 1 0 | red | green | blue |
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`-------------------------------------------------------`
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8-bit tag b11111110
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8-bit red channel value
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8-bit green channel value
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8-bit blue channel value
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The alpha value remains unchanged from the previous pixel.
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.- QOI_OP_RGBA ---------------------------------------------------.
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| Byte[0] | Byte[1] | Byte[2] | Byte[3] | Byte[4] |
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| 7 6 5 4 3 2 1 0 | 7 .. 0 | 7 .. 0 | 7 .. 0 | 7 .. 0 |
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|-------------------------+---------+---------+---------+---------|
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| 1 1 1 1 1 1 1 1 | red | green | blue | alpha |
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`-----------------------------------------------------------------`
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8-bit tag b11111111
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8-bit red channel value
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8-bit green channel value
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8-bit blue channel value
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8-bit alpha channel value
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*/
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/* -----------------------------------------------------------------------------
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Header - Public functions */
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#ifndef QOI_H
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# define QOI_H
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# include "me/mem/mem.h"
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# include "me/mem/mem.h"
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# include "me/types.h"
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/* A pot_i32er to a t_qoi_desc struct has to be supplied to all of qoi's
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functions. It describes either the input format (for qoi_write and qoi_encode),
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or is filled with the description read from the file header (for qoi_read and
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qoi_decode).
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The colorspace in this t_qoi_desc is an enum where
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0 = sRGB, i.e. gamma scaled RGB channels and a linear alpha channel
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1 = all channels are linear
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You may use the constants QOI_SRGB or QOI_LINEAR. The colorspace is purely
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informative. It will be saved to the file header, but does not affect
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how chunks are en-/decoded. */
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# define QOI_SRGB 0
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# define QOI_LINEAR 1
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typedef struct s_t_qoi_desc
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{
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t_u32 width;
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t_u32 height;
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t_u8 channels;
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t_u8 colorspace;
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} t_qoi_desc;
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# ifndef QOI_NO_STDIO
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/* Encode raw RGB or RGBA pixels t_i32o a QOI image and write it to the file
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system. The t_qoi_desc struct must be filled with the image width, height,
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number of channels (3 = RGB, 4 = RGBA) and the colorspace.
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The function returns 0 on failure (invalid parameters, or fopen or malloc
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failed) or the number of bytes written on success. */
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t_i32 qoi_write(t_const_str filename, const void *data,
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const t_qoi_desc *desc);
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/* Read and decode a QOI image from the file system. If channels is 0, the
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number of channels from the file header is used. If channels is 3 or 4 the
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output format will be forced t_i32o this number of channels.
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The function either returns NULL on failure (invalid data, or malloc or fopen
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failed) or a pot_i32er to the decoded pixels. On success, the t_qoi_desc struct
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will be filled with the description from the file header.
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The returned pixel data should be mem_free()d after use. */
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void *qoi_read(t_const_str filename, t_qoi_desc *desc,
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t_i32 channels);
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# endif /* QOI_NO_STDIO */
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/* Encode raw RGB or RGBA pixels t_i32o a QOI image in memory.
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The function either returns NULL on failure (invalid parameters or malloc
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failed) or a pot_i32er to the encoded data on success. On success the out_len
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is set to the size in bytes of the encoded data.
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The returned qoi data should be mem_free()d after use. */
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void *qoi_encode(const void *data, const t_qoi_desc *desc,
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t_i32 *out_len);
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/* Decode a QOI image from memory.
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The function either returns NULL on failure (invalid parameters or malloc
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failed) or a pot_i32er to the decoded pixels. On success, the t_qoi_desc struct
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is filled with the description from the file header.
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The returned pixel data should be mem_free()d after use. */
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void *qoi_decode(const void *data, t_i32 size, t_qoi_desc *desc,
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t_i32 channels);
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#endif /* QOI_H */
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