Add support for QOI format and reading images from memory (#39)

Reviewed-on: #39

include/Refresh_Image.h

@@ -51,20 +51,77 @@ extern "C" {
  * numChannels: Filled with the number of channels in the image.
  *
  * Returns a block of memory suitable for use with Refresh_SetTextureData2D.
- * Be sure to free the memory with Refresh_Image_Free after use!
+ * Be sure to free the memory with Refresh_Image_FreePNG after use!
  */
-REFRESHAPI uint8_t* Refresh_Image_Load(
+REFRESHAPI uint8_t* Refresh_Image_LoadPNGFromFile(
 	char const *filename,
 	int32_t *w,
 	int32_t *h,
 	int32_t *numChannels
 );
 
-/* Frees memory returned by Refresh_Image_Load. (Do NOT free the memory yourself!)
+/* Decodes PNG data into raw RGBA8 texture data.
  *
- * mem: A pointer previously returned by Refresh_Image_Load.
+ * w:		    Filled with the width of the image.
+ * h:		    Filled with the height of the image.
+ * numChannels: Filled with the number of channels in the image.
+ *
+ * Returns a block of memory suitable for use with Refresh_SetTextureData2D.
+ * Be sure to free the memory with Refresh_Image_FreePNG after use!
  */
-REFRESHAPI void Refresh_Image_Free(uint8_t *mem);
+REFRESHAPI uint8_t* Refresh_Image_LoadPNGFromMemory(
+	uint8_t *buffer,
+	int32_t bufferLength,
+	int32_t *w,
+	int32_t *h,
+	int32_t *numChannels
+);
+
+/* Frees memory returned by Refresh_Image_LoadPNG functions. (Do NOT free the memory yourself!)
+ *
+ * mem: A pointer previously returned by Refresh_Image_LoadPNG.
+ */
+REFRESHAPI void Refresh_Image_FreePNG(uint8_t *mem);
+
+/* Decodes QOI data into raw RGBA8 texture data.
+ *
+ * w:		    Filled with the width of the image.
+ * h:		    Filled with the height of the image.
+ * numChannels: Filled with the number of channels in the image.
+ *
+ * Returns a block of memory suitable for use with Refresh_SetTextureData2D.
+ * Be sure to free the memory with Refresh_Image_FreeQOI after use!
+ */
+REFRESHAPI uint8_t* Refresh_Image_LoadQOIFromFile(
+	char const *filename,
+	int32_t *w,
+	int32_t *h,
+	int32_t *numChannels
+);
+
+/* Decodes QOI data into raw RGBA8 texture data.
+ *
+ * bufferLength: The length of the input buffer to be decoded.
+ * w:		     Filled with the width of the image.
+ * h:		     Filled with the height of the image.
+ * numChannels:  Filled with the number of channels in the image.
+ *
+ * Returns a block of memory suitable for use with Refresh_SetTextureData2D.
+ * Be sure to free the memory with Refresh_Image_FreeQOI after use!
+ */
+REFRESHAPI uint8_t* Refresh_Image_LoadQOIFromMemory(
+	uint8_t *buffer,
+	int32_t bufferLength,
+	int32_t *w,
+	int32_t *h,
+	int32_t *numChannels
+);
+
+/* Frees memory returned by Refresh_Image_LoadQOI functions. (Do NOT free the memory yourself!)
+ *
+ * mem: A pointer previously returned by Refresh_Image_LoadQOI.
+ */
+REFRESHAPI void Refresh_Image_FreeQOI(uint8_t *mem);
 
 /* Image Write API */
 
@@ -84,6 +141,20 @@ REFRESHAPI void Refresh_Image_SavePNG(
 	uint8_t *data
 );
 
+/* Encodes 32-bit color data into PNG data.
+ *
+ * filename:    The filename that the image will be written to.
+ * w:	        The width of the PNG data.
+ * h:	        The height of the PNG data.
+ * data:	    The raw color data.
+ */
+REFRESHAPI void Refresh_Image_SaveQOI(
+	char const *filename,
+	int32_t w,
+	int32_t h,
+	uint8_t *data
+);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */

src/Refresh_Image.c

@@ -48,7 +48,6 @@
 #define floorf SDL_floorf
 #define ldexp SDL_scalbn
 #define pow SDL_pow
-#define strtol SDL_strtol
 
 #ifdef memcmp
 #undef memcmp
@@ -74,10 +73,6 @@
 #undef strlen
 #endif
 #define strlen SDL_strlen
-#ifdef strncmp
-#undef strncmp
-#endif
-#define strncmp SDL_strncmp
 
 /* These are per the Texture2D.FromStream spec */
 #define STBI_ONLY_PNG
@@ -140,6 +135,7 @@ SDL_SIMDRealloc(void *mem, const size_t len)
 #endif
 
 #define STB_IMAGE_STATIC
+#define STBI_NO_HDR
 #define STBI_ASSERT SDL_assert
 #define STBI_MALLOC SDL_SIMDAlloc
 #define STBI_REALLOC SDL_SIMDRealloc
@@ -150,6 +146,12 @@ SDL_SIMDRealloc(void *mem, const size_t len)
 #endif
 #include "stb_image.h"
 
+#define QOI_IMPLEMENTATION
+#define QOI_MALLOC SDL_SIMDAlloc
+#define QOI_FREE SDL_SIMDFree
+#define QOI_ZEROARR SDL_zero
+#include "qoi.h"
+
 #define MINIZ_NO_STDIO
 #define MINIZ_NO_TIME
 #define MINIZ_SDL_MALLOC
@@ -189,7 +191,7 @@ static unsigned char* dgibson_stbi_zlib_compress(
 
 /* Image Read API */
 
-uint8_t* Refresh_Image_Load(
+uint8_t* Refresh_Image_LoadPNGFromFile(
 	char const *filename,
 	int32_t *w,
 	int32_t *h,
@@ -198,11 +200,55 @@ uint8_t* Refresh_Image_Load(
 	return stbi_load(filename, w, h, numChannels, STBI_rgb_alpha);
 }
 
-void Refresh_Image_Free(uint8_t *mem)
+uint8_t* Refresh_Image_LoadPNGFromMemory(
+	uint8_t *buffer,
+	int32_t bufferLength,
+	int32_t *w,
+	int32_t *h,
+	int32_t *numChannels
+) {
+	return stbi_load_from_memory(buffer, bufferLength, w, h, numChannels, STBI_rgb_alpha);
+}
+
+void Refresh_Image_FreePNG(uint8_t *mem)
 {
 	stbi_image_free(mem);
 }
 
+uint8_t *Refresh_Image_LoadQOIFromFile(
+	char const *filename,
+	int32_t *w,
+	int32_t *h,
+	int32_t *numChannels
+) {
+	qoi_desc desc;
+	uint8_t *pixels = qoi_read(filename, &desc, 0);
+	*w = desc.width;
+	*h = desc.height;
+	*numChannels = desc.channels;
+	return pixels;
+}
+
+uint8_t* Refresh_Image_LoadQOIFromMemory(
+	uint8_t *buffer,
+	int32_t bufferLength,
+	int32_t *w,
+	int32_t *h,
+	int32_t *numChannels
+) {
+	qoi_desc desc;
+	uint8_t *pixels = qoi_decode(buffer, bufferLength, &desc, 0);
+	*w = desc.width;
+	*h = desc.height;
+	*numChannels = desc.channels;
+	return pixels;
+}
+
+void Refresh_Image_FreeQOI(uint8_t *mem)
+{
+	QOI_FREE(mem);
+}
+
 /* Image Write API */
 
 void Refresh_Image_SavePNG(
@@ -237,4 +283,18 @@ void Refresh_Image_SavePNG(
 	}
 }
 
+void Refresh_Image_SaveQOI(
+	char const *filename,
+	int32_t w,
+	int32_t h,
+	uint8_t *data
+) {
+	qoi_desc desc;
+	desc.width = w;
+	desc.height = h;
+	desc.channels = 4;
+	desc.colorspace = QOI_LINEAR;
+	qoi_write(filename, data, &desc);
+}
+
 /* vim: set noexpandtab shiftwidth=8 tabstop=8: */

src/qoi.h

@@ -0,0 +1,649 @@
+/*
+
+Copyright (c) 2021, Dominic Szablewski - https://phoboslab.org
+SPDX-License-Identifier: MIT
+
+
+QOI - The "Quite OK Image" format for fast, lossless image compression
+
+-- About
+
+QOI encodes and decodes images in a lossless format. Compared to stb_image and
+stb_image_write QOI offers 20x-50x faster encoding, 3x-4x faster decoding and
+20% better compression.
+
+
+-- Synopsis
+
+// Define `QOI_IMPLEMENTATION` in *one* C/C++ file before including this
+// library to create the implementation.
+
+#define QOI_IMPLEMENTATION
+#include "qoi.h"
+
+// Encode and store an RGBA buffer to the file system. The qoi_desc describes
+// the input pixel data.
+qoi_write("image_new.qoi", rgba_pixels, &(qoi_desc){
+	.width = 1920,
+	.height = 1080,
+	.channels = 4,
+	.colorspace = QOI_SRGB
+});
+
+// Load and decode a QOI image from the file system into a 32bbp RGBA buffer.
+// The qoi_desc struct will be filled with the width, height, number of channels
+// and colorspace read from the file header.
+qoi_desc desc;
+void *rgba_pixels = qoi_read("image.qoi", &desc, 4);
+
+
+
+-- Documentation
+
+This library provides the following functions;
+- qoi_read    -- read and decode a QOI file
+- qoi_decode  -- decode the raw bytes of a QOI image from memory
+- qoi_write   -- encode and write a QOI file
+- qoi_encode  -- encode an rgba buffer into a QOI image in memory
+
+See the function declaration below for the signature and more information.
+
+If you don't want/need the qoi_read and qoi_write functions, you can define
+QOI_NO_STDIO before including this library.
+
+This library uses malloc() and free(). To supply your own malloc implementation
+you can define QOI_MALLOC and QOI_FREE before including this library.
+
+This library uses memset() to zero-initialize the index. To supply your own
+implementation you can define QOI_ZEROARR before including this library.
+
+
+-- Data Format
+
+A QOI file has a 14 byte header, followed by any number of data "chunks" and an
+8-byte end marker.
+
+struct qoi_header_t {
+	char     magic[4];   // magic bytes "qoif"
+	uint32_t width;      // image width in pixels (BE)
+	uint32_t height;     // image height in pixels (BE)
+	uint8_t  channels;   // 3 = RGB, 4 = RGBA
+	uint8_t  colorspace; // 0 = sRGB with linear alpha, 1 = all channels linear
+};
+
+Images are encoded row by row, left to right, top to bottom. The decoder and
+encoder start with {r: 0, g: 0, b: 0, a: 255} as the previous pixel value. An
+image is complete when all pixels specified by width * height have been covered.
+
+Pixels are encoded as
+ - a run of the previous pixel
+ - an index into an array of previously seen pixels
+ - a difference to the previous pixel value in r,g,b
+ - full r,g,b or r,g,b,a values
+
+The color channels are assumed to not be premultiplied with the alpha channel
+("un-premultiplied alpha").
+
+A running array[64] (zero-initialized) of previously seen pixel values is
+maintained by the encoder and decoder. Each pixel that is seen by the encoder
+and decoder is put into this array at the position formed by a hash function of
+the color value. In the encoder, if the pixel value at the index matches the
+current pixel, this index position is written to the stream as QOI_OP_INDEX.
+The hash function for the index is:
+
+	index_position = (r * 3 + g * 5 + b * 7 + a * 11) % 64
+
+Each chunk starts with a 2- or 8-bit tag, followed by a number of data bits. The
+bit length of chunks is divisible by 8 - i.e. all chunks are byte aligned. All
+values encoded in these data bits have the most significant bit on the left.
+
+The 8-bit tags have precedence over the 2-bit tags. A decoder must check for the
+presence of an 8-bit tag first.
+
+The byte stream's end is marked with 7 0x00 bytes followed a single 0x01 byte.
+
+
+The possible chunks are:
+
+
+.- QOI_OP_INDEX ----------.
+|         Byte[0]         |
+|  7  6  5  4  3  2  1  0 |
+|-------+-----------------|
+|  0  0 |     index       |
+`-------------------------`
+2-bit tag b00
+6-bit index into the color index array: 0..63
+
+A valid encoder must not issue 2 or more consecutive QOI_OP_INDEX chunks to the
+same index. QOI_OP_RUN should be used instead.
+
+
+.- QOI_OP_DIFF -----------.
+|         Byte[0]         |
+|  7  6  5  4  3  2  1  0 |
+|-------+-----+-----+-----|
+|  0  1 |  dr |  dg |  db |
+`-------------------------`
+2-bit tag b01
+2-bit   red channel difference from the previous pixel between -2..1
+2-bit green channel difference from the previous pixel between -2..1
+2-bit  blue channel difference from the previous pixel between -2..1
+
+The difference to the current channel values are using a wraparound operation,
+so "1 - 2" will result in 255, while "255 + 1" will result in 0.
+
+Values are stored as unsigned integers with a bias of 2. E.g. -2 is stored as
+0 (b00). 1 is stored as 3 (b11).
+
+The alpha value remains unchanged from the previous pixel.
+
+
+.- QOI_OP_LUMA -------------------------------------.
+|         Byte[0]         |         Byte[1]         |
+|  7  6  5  4  3  2  1  0 |  7  6  5  4  3  2  1  0 |
+|-------+-----------------+-------------+-----------|
+|  1  0 |  green diff     |   dr - dg   |  db - dg  |
+`---------------------------------------------------`
+2-bit tag b10
+6-bit green channel difference from the previous pixel -32..31
+4-bit   red channel difference minus green channel difference -8..7
+4-bit  blue channel difference minus green channel difference -8..7
+
+The green channel is used to indicate the general direction of change and is
+encoded in 6 bits. The red and blue channels (dr and db) base their diffs off
+of the green channel difference and are encoded in 4 bits. I.e.:
+	dr_dg = (cur_px.r - prev_px.r) - (cur_px.g - prev_px.g)
+	db_dg = (cur_px.b - prev_px.b) - (cur_px.g - prev_px.g)
+
+The difference to the current channel values are using a wraparound operation,
+so "10 - 13" will result in 253, while "250 + 7" will result in 1.
+
+Values are stored as unsigned integers with a bias of 32 for the green channel
+and a bias of 8 for the red and blue channel.
+
+The alpha value remains unchanged from the previous pixel.
+
+
+.- QOI_OP_RUN ------------.
+|         Byte[0]         |
+|  7  6  5  4  3  2  1  0 |
+|-------+-----------------|
+|  1  1 |       run       |
+`-------------------------`
+2-bit tag b11
+6-bit run-length repeating the previous pixel: 1..62
+
+The run-length is stored with a bias of -1. Note that the run-lengths 63 and 64
+(b111110 and b111111) are illegal as they are occupied by the QOI_OP_RGB and
+QOI_OP_RGBA tags.
+
+
+.- QOI_OP_RGB ------------------------------------------.
+|         Byte[0]         | Byte[1] | Byte[2] | Byte[3] |
+|  7  6  5  4  3  2  1  0 | 7 .. 0  | 7 .. 0  | 7 .. 0  |
+|-------------------------+---------+---------+---------|
+|  1  1  1  1  1  1  1  0 |   red   |  green  |  blue   |
+`-------------------------------------------------------`
+8-bit tag b11111110
+8-bit   red channel value
+8-bit green channel value
+8-bit  blue channel value
+
+The alpha value remains unchanged from the previous pixel.
+
+
+.- QOI_OP_RGBA ---------------------------------------------------.
+|         Byte[0]         | Byte[1] | Byte[2] | Byte[3] | Byte[4] |
+|  7  6  5  4  3  2  1  0 | 7 .. 0  | 7 .. 0  | 7 .. 0  | 7 .. 0  |
+|-------------------------+---------+---------+---------+---------|
+|  1  1  1  1  1  1  1  1 |   red   |  green  |  blue   |  alpha  |
+`-----------------------------------------------------------------`
+8-bit tag b11111111
+8-bit   red channel value
+8-bit green channel value
+8-bit  blue channel value
+8-bit alpha channel value
+
+*/
+
+
+/* -----------------------------------------------------------------------------
+Header - Public functions */
+
+#ifndef QOI_H
+#define QOI_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* A pointer to a qoi_desc struct has to be supplied to all of qoi's functions.
+It describes either the input format (for qoi_write and qoi_encode), or is
+filled with the description read from the file header (for qoi_read and
+qoi_decode).
+
+The colorspace in this qoi_desc is an enum where
+	0 = sRGB, i.e. gamma scaled RGB channels and a linear alpha channel
+	1 = all channels are linear
+You may use the constants QOI_SRGB or QOI_LINEAR. The colorspace is purely
+informative. It will be saved to the file header, but does not affect
+how chunks are en-/decoded. */
+
+#define QOI_SRGB   0
+#define QOI_LINEAR 1
+
+typedef struct {
+	unsigned int width;
+	unsigned int height;
+	unsigned char channels;
+	unsigned char colorspace;
+} qoi_desc;
+
+#ifndef QOI_NO_STDIO
+
+/* Encode raw RGB or RGBA pixels into a QOI image and write it to the file
+system. The qoi_desc struct must be filled with the image width, height,
+number of channels (3 = RGB, 4 = RGBA) and the colorspace.
+
+The function returns 0 on failure (invalid parameters, or fopen or malloc
+failed) or the number of bytes written on success. */
+
+int qoi_write(const char *filename, const void *data, const qoi_desc *desc);
+
+
+/* Read and decode a QOI image from the file system. If channels is 0, the
+number of channels from the file header is used. If channels is 3 or 4 the
+output format will be forced into this number of channels.
+
+The function either returns NULL on failure (invalid data, or malloc or fopen
+failed) or a pointer to the decoded pixels. On success, the qoi_desc struct
+will be filled with the description from the file header.
+
+The returned pixel data should be free()d after use. */
+
+void *qoi_read(const char *filename, qoi_desc *desc, int channels);
+
+#endif /* QOI_NO_STDIO */
+
+
+/* Encode raw RGB or RGBA pixels into a QOI image in memory.
+
+The function either returns NULL on failure (invalid parameters or malloc
+failed) or a pointer to the encoded data on success. On success the out_len
+is set to the size in bytes of the encoded data.
+
+The returned qoi data should be free()d after use. */
+
+void *qoi_encode(const void *data, const qoi_desc *desc, int *out_len);
+
+
+/* Decode a QOI image from memory.
+
+The function either returns NULL on failure (invalid parameters or malloc
+failed) or a pointer to the decoded pixels. On success, the qoi_desc struct
+is filled with the description from the file header.
+
+The returned pixel data should be free()d after use. */
+
+void *qoi_decode(const void *data, int size, qoi_desc *desc, int channels);
+
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* QOI_H */
+
+
+/* -----------------------------------------------------------------------------
+Implementation */
+
+#ifdef QOI_IMPLEMENTATION
+#include <stdlib.h>
+#include <string.h>
+
+#ifndef QOI_MALLOC
+	#define QOI_MALLOC(sz) malloc(sz)
+	#define QOI_FREE(p)    free(p)
+#endif
+#ifndef QOI_ZEROARR
+	#define QOI_ZEROARR(a) memset((a),0,sizeof(a))
+#endif
+
+#define QOI_OP_INDEX  0x00 /* 00xxxxxx */
+#define QOI_OP_DIFF   0x40 /* 01xxxxxx */
+#define QOI_OP_LUMA   0x80 /* 10xxxxxx */
+#define QOI_OP_RUN    0xc0 /* 11xxxxxx */
+#define QOI_OP_RGB    0xfe /* 11111110 */
+#define QOI_OP_RGBA   0xff /* 11111111 */
+
+#define QOI_MASK_2    0xc0 /* 11000000 */
+
+#define QOI_COLOR_HASH(C) (C.rgba.r*3 + C.rgba.g*5 + C.rgba.b*7 + C.rgba.a*11)
+#define QOI_MAGIC \
+	(((unsigned int)'q') << 24 | ((unsigned int)'o') << 16 | \
+	 ((unsigned int)'i') <<  8 | ((unsigned int)'f'))
+#define QOI_HEADER_SIZE 14
+
+/* 2GB is the max file size that this implementation can safely handle. We guard
+against anything larger than that, assuming the worst case with 5 bytes per
+pixel, rounded down to a nice clean value. 400 million pixels ought to be
+enough for anybody. */
+#define QOI_PIXELS_MAX ((unsigned int)400000000)
+
+typedef union {
+	struct { unsigned char r, g, b, a; } rgba;
+	unsigned int v;
+} qoi_rgba_t;
+
+static const unsigned char qoi_padding[8] = {0,0,0,0,0,0,0,1};
+
+static void qoi_write_32(unsigned char *bytes, int *p, unsigned int v) {
+	bytes[(*p)++] = (0xff000000 & v) >> 24;
+	bytes[(*p)++] = (0x00ff0000 & v) >> 16;
+	bytes[(*p)++] = (0x0000ff00 & v) >> 8;
+	bytes[(*p)++] = (0x000000ff & v);
+}
+
+static unsigned int qoi_read_32(const unsigned char *bytes, int *p) {
+	unsigned int a = bytes[(*p)++];
+	unsigned int b = bytes[(*p)++];
+	unsigned int c = bytes[(*p)++];
+	unsigned int d = bytes[(*p)++];
+	return a << 24 | b << 16 | c << 8 | d;
+}
+
+void *qoi_encode(const void *data, const qoi_desc *desc, int *out_len) {
+	int i, max_size, p, run;
+	int px_len, px_end, px_pos, channels;
+	unsigned char *bytes;
+	const unsigned char *pixels;
+	qoi_rgba_t index[64];
+	qoi_rgba_t px, px_prev;
+
+	if (
+		data == NULL || out_len == NULL || desc == NULL ||
+		desc->width == 0 || desc->height == 0 ||
+		desc->channels < 3 || desc->channels > 4 ||
+		desc->colorspace > 1 ||
+		desc->height >= QOI_PIXELS_MAX / desc->width
+	) {
+		return NULL;
+	}
+
+	max_size =
+		desc->width * desc->height * (desc->channels + 1) +
+		QOI_HEADER_SIZE + sizeof(qoi_padding);
+
+	p = 0;
+	bytes = (unsigned char *) QOI_MALLOC(max_size);
+	if (!bytes) {
+		return NULL;
+	}
+
+	qoi_write_32(bytes, &p, QOI_MAGIC);
+	qoi_write_32(bytes, &p, desc->width);
+	qoi_write_32(bytes, &p, desc->height);
+	bytes[p++] = desc->channels;
+	bytes[p++] = desc->colorspace;
+
+
+	pixels = (const unsigned char *)data;
+
+	QOI_ZEROARR(index);
+
+	run = 0;
+	px_prev.rgba.r = 0;
+	px_prev.rgba.g = 0;
+	px_prev.rgba.b = 0;
+	px_prev.rgba.a = 255;
+	px = px_prev;
+
+	px_len = desc->width * desc->height * desc->channels;
+	px_end = px_len - desc->channels;
+	channels = desc->channels;
+
+	for (px_pos = 0; px_pos < px_len; px_pos += channels) {
+		px.rgba.r = pixels[px_pos + 0];
+		px.rgba.g = pixels[px_pos + 1];
+		px.rgba.b = pixels[px_pos + 2];
+
+		if (channels == 4) {
+			px.rgba.a = pixels[px_pos + 3];
+		}
+
+		if (px.v == px_prev.v) {
+			run++;
+			if (run == 62 || px_pos == px_end) {
+				bytes[p++] = QOI_OP_RUN | (run - 1);
+				run = 0;
+			}
+		}
+		else {
+			int index_pos;
+
+			if (run > 0) {
+				bytes[p++] = QOI_OP_RUN | (run - 1);
+				run = 0;
+			}
+
+			index_pos = QOI_COLOR_HASH(px) % 64;
+
+			if (index[index_pos].v == px.v) {
+				bytes[p++] = QOI_OP_INDEX | index_pos;
+			}
+			else {
+				index[index_pos] = px;
+
+				if (px.rgba.a == px_prev.rgba.a) {
+					signed char vr = px.rgba.r - px_prev.rgba.r;
+					signed char vg = px.rgba.g - px_prev.rgba.g;
+					signed char vb = px.rgba.b - px_prev.rgba.b;
+
+					signed char vg_r = vr - vg;
+					signed char vg_b = vb - vg;
+
+					if (
+						vr > -3 && vr < 2 &&
+						vg > -3 && vg < 2 &&
+						vb > -3 && vb < 2
+					) {
+						bytes[p++] = QOI_OP_DIFF | (vr + 2) << 4 | (vg + 2) << 2 | (vb + 2);
+					}
+					else if (
+						vg_r >  -9 && vg_r <  8 &&
+						vg   > -33 && vg   < 32 &&
+						vg_b >  -9 && vg_b <  8
+					) {
+						bytes[p++] = QOI_OP_LUMA     | (vg   + 32);
+						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 */