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src/qoi.h
649
src/qoi.h
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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 qoi_desc describes
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// the input pixel data.
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qoi_write("image_new.qoi", rgba_pixels, &(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 into a 32bbp RGBA buffer.
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// The qoi_desc struct will be filled with the width, height, number of channels
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// and colorspace read from the file header.
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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 into 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 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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uint32_t width; // image width in pixels (BE)
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uint32_t height; // image height in pixels (BE)
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uint8_t channels; // 3 = RGB, 4 = RGBA
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uint8_t colorspace; // 0 = sRGB with linear alpha, 1 = all channels 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 into 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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maintained by the encoder and decoder. Each pixel that is seen by the encoder
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and decoder is put into this array at the position formed by a hash function of
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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 into 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 integers 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 integers 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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#ifdef __cplusplus
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extern "C" {
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#endif
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/* A pointer to a qoi_desc struct has to be supplied to all of qoi's functions.
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It describes either the input format (for qoi_write and qoi_encode), or is
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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 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 {
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unsigned int width;
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unsigned int height;
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unsigned char channels;
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unsigned char colorspace;
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} qoi_desc;
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#ifndef QOI_NO_STDIO
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/* Encode raw RGB or RGBA pixels into a QOI image and write it to the file
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system. The 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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int qoi_write(const char *filename, const void *data, const 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 into 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 pointer to the decoded pixels. On success, the 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 free()d after use. */
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void *qoi_read(const char *filename, qoi_desc *desc, int channels);
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#endif /* QOI_NO_STDIO */
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/* Encode raw RGB or RGBA pixels into 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 pointer 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 free()d after use. */
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void *qoi_encode(const void *data, const qoi_desc *desc, int *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 pointer to the decoded pixels. On success, the 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 free()d after use. */
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void *qoi_decode(const void *data, int size, qoi_desc *desc, int channels);
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#ifdef __cplusplus
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}
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#endif
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#endif /* QOI_H */
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/* -----------------------------------------------------------------------------
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Implementation */
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#ifdef QOI_IMPLEMENTATION
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#include <stdlib.h>
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#include <string.h>
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#ifndef QOI_MALLOC
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#define QOI_MALLOC(sz) malloc(sz)
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#define QOI_FREE(p) free(p)
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#endif
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#ifndef QOI_ZEROARR
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#define QOI_ZEROARR(a) memset((a),0,sizeof(a))
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#endif
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#define QOI_OP_INDEX 0x00 /* 00xxxxxx */
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#define QOI_OP_DIFF 0x40 /* 01xxxxxx */
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#define QOI_OP_LUMA 0x80 /* 10xxxxxx */
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#define QOI_OP_RUN 0xc0 /* 11xxxxxx */
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#define QOI_OP_RGB 0xfe /* 11111110 */
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#define QOI_OP_RGBA 0xff /* 11111111 */
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#define QOI_MASK_2 0xc0 /* 11000000 */
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#define QOI_COLOR_HASH(C) (C.rgba.r*3 + C.rgba.g*5 + C.rgba.b*7 + C.rgba.a*11)
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#define QOI_MAGIC \
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(((unsigned int)'q') << 24 | ((unsigned int)'o') << 16 | \
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((unsigned int)'i') << 8 | ((unsigned int)'f'))
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#define QOI_HEADER_SIZE 14
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/* 2GB is the max file size that this implementation can safely handle. We guard
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against anything larger than that, assuming the worst case with 5 bytes per
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pixel, rounded down to a nice clean value. 400 million pixels ought to be
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enough for anybody. */
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#define QOI_PIXELS_MAX ((unsigned int)400000000)
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typedef union {
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struct { unsigned char r, g, b, a; } rgba;
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unsigned int v;
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} qoi_rgba_t;
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static const unsigned char qoi_padding[8] = {0,0,0,0,0,0,0,1};
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static void qoi_write_32(unsigned char *bytes, int *p, unsigned int v) {
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bytes[(*p)++] = (0xff000000 & v) >> 24;
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bytes[(*p)++] = (0x00ff0000 & v) >> 16;
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bytes[(*p)++] = (0x0000ff00 & v) >> 8;
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bytes[(*p)++] = (0x000000ff & v);
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}
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static unsigned int qoi_read_32(const unsigned char *bytes, int *p) {
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unsigned int a = bytes[(*p)++];
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unsigned int b = bytes[(*p)++];
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unsigned int c = bytes[(*p)++];
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unsigned int d = bytes[(*p)++];
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return a << 24 | b << 16 | c << 8 | d;
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}
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void *qoi_encode(const void *data, const qoi_desc *desc, int *out_len) {
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int i, max_size, p, run;
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int px_len, px_end, px_pos, channels;
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unsigned char *bytes;
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const unsigned char *pixels;
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qoi_rgba_t index[64];
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qoi_rgba_t px, px_prev;
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if (
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data == NULL || out_len == NULL || desc == NULL ||
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desc->width == 0 || desc->height == 0 ||
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desc->channels < 3 || desc->channels > 4 ||
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desc->colorspace > 1 ||
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desc->height >= QOI_PIXELS_MAX / desc->width
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) {
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return NULL;
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}
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max_size =
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desc->width * desc->height * (desc->channels + 1) +
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QOI_HEADER_SIZE + sizeof(qoi_padding);
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p = 0;
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bytes = (unsigned char *) QOI_MALLOC(max_size);
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if (!bytes) {
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return NULL;
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}
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qoi_write_32(bytes, &p, QOI_MAGIC);
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qoi_write_32(bytes, &p, desc->width);
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qoi_write_32(bytes, &p, desc->height);
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bytes[p++] = desc->channels;
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bytes[p++] = desc->colorspace;
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pixels = (const unsigned char *)data;
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QOI_ZEROARR(index);
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run = 0;
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px_prev.rgba.r = 0;
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px_prev.rgba.g = 0;
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px_prev.rgba.b = 0;
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px_prev.rgba.a = 255;
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px = px_prev;
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px_len = desc->width * desc->height * desc->channels;
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px_end = px_len - desc->channels;
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channels = desc->channels;
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for (px_pos = 0; px_pos < px_len; px_pos += channels) {
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px.rgba.r = pixels[px_pos + 0];
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px.rgba.g = pixels[px_pos + 1];
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px.rgba.b = pixels[px_pos + 2];
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if (channels == 4) {
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px.rgba.a = pixels[px_pos + 3];
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}
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if (px.v == px_prev.v) {
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run++;
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if (run == 62 || px_pos == px_end) {
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bytes[p++] = QOI_OP_RUN | (run - 1);
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run = 0;
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}
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}
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else {
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int index_pos;
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if (run > 0) {
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bytes[p++] = QOI_OP_RUN | (run - 1);
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run = 0;
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}
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index_pos = QOI_COLOR_HASH(px) % 64;
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if (index[index_pos].v == px.v) {
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bytes[p++] = QOI_OP_INDEX | index_pos;
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}
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else {
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index[index_pos] = px;
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if (px.rgba.a == px_prev.rgba.a) {
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signed char vr = px.rgba.r - px_prev.rgba.r;
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signed char vg = px.rgba.g - px_prev.rgba.g;
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signed char vb = px.rgba.b - px_prev.rgba.b;
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signed char vg_r = vr - vg;
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signed char vg_b = vb - vg;
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if (
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vr > -3 && vr < 2 &&
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vg > -3 && vg < 2 &&
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vb > -3 && vb < 2
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) {
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bytes[p++] = QOI_OP_DIFF | (vr + 2) << 4 | (vg + 2) << 2 | (vb + 2);
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}
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else if (
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vg_r > -9 && vg_r < 8 &&
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vg > -33 && vg < 32 &&
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vg_b > -9 && vg_b < 8
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) {
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bytes[p++] = QOI_OP_LUMA | (vg + 32);
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bytes[p++] = (vg_r + 8) << 4 | (vg_b + 8);
|
||||
}
|
||||
else {
|
||||
bytes[p++] = QOI_OP_RGB;
|
||||
bytes[p++] = px.rgba.r;
|
||||
bytes[p++] = px.rgba.g;
|
||||
bytes[p++] = px.rgba.b;
|
||||
}
|
||||
}
|
||||
else {
|
||||
bytes[p++] = QOI_OP_RGBA;
|
||||
bytes[p++] = px.rgba.r;
|
||||
bytes[p++] = px.rgba.g;
|
||||
bytes[p++] = px.rgba.b;
|
||||
bytes[p++] = px.rgba.a;
|
||||
}
|
||||
}
|
||||
}
|
||||
px_prev = px;
|
||||
}
|
||||
|
||||
for (i = 0; i < (int)sizeof(qoi_padding); i++) {
|
||||
bytes[p++] = qoi_padding[i];
|
||||
}
|
||||
|
||||
*out_len = p;
|
||||
return bytes;
|
||||
}
|
||||
|
||||
void *qoi_decode(const void *data, int size, qoi_desc *desc, int channels) {
|
||||
const unsigned char *bytes;
|
||||
unsigned int header_magic;
|
||||
unsigned char *pixels;
|
||||
qoi_rgba_t index[64];
|
||||
qoi_rgba_t px;
|
||||
int px_len, chunks_len, px_pos;
|
||||
int p = 0, run = 0;
|
||||
|
||||
if (
|
||||
data == NULL || desc == NULL ||
|
||||
(channels != 0 && channels != 3 && channels != 4) ||
|
||||
size < QOI_HEADER_SIZE + (int)sizeof(qoi_padding)
|
||||
) {
|
||||
return NULL;
|
||||
}
|
||||
|
||||
bytes = (const unsigned char *)data;
|
||||
|
||||
header_magic = qoi_read_32(bytes, &p);
|
||||
desc->width = qoi_read_32(bytes, &p);
|
||||
desc->height = qoi_read_32(bytes, &p);
|
||||
desc->channels = bytes[p++];
|
||||
desc->colorspace = bytes[p++];
|
||||
|
||||
if (
|
||||
desc->width == 0 || desc->height == 0 ||
|
||||
desc->channels < 3 || desc->channels > 4 ||
|
||||
desc->colorspace > 1 ||
|
||||
header_magic != QOI_MAGIC ||
|
||||
desc->height >= QOI_PIXELS_MAX / desc->width
|
||||
) {
|
||||
return NULL;
|
||||
}
|
||||
|
||||
if (channels == 0) {
|
||||
channels = desc->channels;
|
||||
}
|
||||
|
||||
px_len = desc->width * desc->height * channels;
|
||||
pixels = (unsigned char *) QOI_MALLOC(px_len);
|
||||
if (!pixels) {
|
||||
return NULL;
|
||||
}
|
||||
|
||||
QOI_ZEROARR(index);
|
||||
px.rgba.r = 0;
|
||||
px.rgba.g = 0;
|
||||
px.rgba.b = 0;
|
||||
px.rgba.a = 255;
|
||||
|
||||
chunks_len = size - (int)sizeof(qoi_padding);
|
||||
for (px_pos = 0; px_pos < px_len; px_pos += channels) {
|
||||
if (run > 0) {
|
||||
run--;
|
||||
}
|
||||
else if (p < chunks_len) {
|
||||
int b1 = bytes[p++];
|
||||
|
||||
if (b1 == QOI_OP_RGB) {
|
||||
px.rgba.r = bytes[p++];
|
||||
px.rgba.g = bytes[p++];
|
||||
px.rgba.b = bytes[p++];
|
||||
}
|
||||
else if (b1 == QOI_OP_RGBA) {
|
||||
px.rgba.r = bytes[p++];
|
||||
px.rgba.g = bytes[p++];
|
||||
px.rgba.b = bytes[p++];
|
||||
px.rgba.a = bytes[p++];
|
||||
}
|
||||
else if ((b1 & QOI_MASK_2) == QOI_OP_INDEX) {
|
||||
px = index[b1];
|
||||
}
|
||||
else if ((b1 & QOI_MASK_2) == QOI_OP_DIFF) {
|
||||
px.rgba.r += ((b1 >> 4) & 0x03) - 2;
|
||||
px.rgba.g += ((b1 >> 2) & 0x03) - 2;
|
||||
px.rgba.b += ( b1 & 0x03) - 2;
|
||||
}
|
||||
else if ((b1 & QOI_MASK_2) == QOI_OP_LUMA) {
|
||||
int b2 = bytes[p++];
|
||||
int vg = (b1 & 0x3f) - 32;
|
||||
px.rgba.r += vg - 8 + ((b2 >> 4) & 0x0f);
|
||||
px.rgba.g += vg;
|
||||
px.rgba.b += vg - 8 + (b2 & 0x0f);
|
||||
}
|
||||
else if ((b1 & QOI_MASK_2) == QOI_OP_RUN) {
|
||||
run = (b1 & 0x3f);
|
||||
}
|
||||
|
||||
index[QOI_COLOR_HASH(px) % 64] = px;
|
||||
}
|
||||
|
||||
pixels[px_pos + 0] = px.rgba.r;
|
||||
pixels[px_pos + 1] = px.rgba.g;
|
||||
pixels[px_pos + 2] = px.rgba.b;
|
||||
|
||||
if (channels == 4) {
|
||||
pixels[px_pos + 3] = px.rgba.a;
|
||||
}
|
||||
}
|
||||
|
||||
return pixels;
|
||||
}
|
||||
|
||||
#ifndef QOI_NO_STDIO
|
||||
#include <stdio.h>
|
||||
|
||||
int qoi_write(const char *filename, const void *data, const qoi_desc *desc) {
|
||||
FILE *f = fopen(filename, "wb");
|
||||
int size;
|
||||
void *encoded;
|
||||
|
||||
if (!f) {
|
||||
return 0;
|
||||
}
|
||||
|
||||
encoded = qoi_encode(data, desc, &size);
|
||||
if (!encoded) {
|
||||
fclose(f);
|
||||
return 0;
|
||||
}
|
||||
|
||||
fwrite(encoded, 1, size, f);
|
||||
fclose(f);
|
||||
|
||||
QOI_FREE(encoded);
|
||||
return size;
|
||||
}
|
||||
|
||||
void *qoi_read(const char *filename, qoi_desc *desc, int channels) {
|
||||
FILE *f = fopen(filename, "rb");
|
||||
int size, bytes_read;
|
||||
void *pixels, *data;
|
||||
|
||||
if (!f) {
|
||||
return NULL;
|
||||
}
|
||||
|
||||
fseek(f, 0, SEEK_END);
|
||||
size = ftell(f);
|
||||
if (size <= 0) {
|
||||
fclose(f);
|
||||
return NULL;
|
||||
}
|
||||
fseek(f, 0, SEEK_SET);
|
||||
|
||||
data = QOI_MALLOC(size);
|
||||
if (!data) {
|
||||
fclose(f);
|
||||
return NULL;
|
||||
}
|
||||
|
||||
bytes_read = fread(data, 1, size, f);
|
||||
fclose(f);
|
||||
|
||||
pixels = qoi_decode(data, bytes_read, desc, channels);
|
||||
QOI_FREE(data);
|
||||
return pixels;
|
||||
}
|
||||
|
||||
#endif /* QOI_NO_STDIO */
|
||||
#endif /* QOI_IMPLEMENTATION */
|
||||
Loading…
Reference in New Issue