Add pamtoqoi, qoitopam, raw submission

git-svn-id: http://svn.code.sf.net/p/netpbm/code/trunk@4339 9d0c8265-081b-0410-96cb-a4ca84ce46f8

5 files changed, 982 insertions, 4 deletions

diff --git a/converter/other/Makefile b/converter/other/Makefile
index 5dfc27ec..b1f8461a 100644
--- a/converter/other/Makefile
+++ b/converter/other/Makefile
@@ -134,14 +134,15 @@ PORTBINARIES =  avstopam bmptopnm fitstopnm \
 		gemtopnm giftopnm hdifftopam infotopam \
 		pamtoavs pamtodjvurle pamtofits pamtogif \
 		pamtohdiff pamtohtmltbl pamtompfont pamtooctaveimg \
-		pamtopam pamtopdbimg pamtopfm pamtopnm pamtosrf pamtouil \
+		pamtopam pamtopdbimg pamtopfm pamtopnm \
+                pamtoqoi pamtosrf pamtouil \
 		pamtowinicon pamtoxvmini \
 		pbmtopgm pdbimgtopam pfmtopam \
 	        pgmtopbm pgmtoppm ppmtopgm pnmtoddif \
 		pnmtopclxl pnmtorast \
-		pnmtosgi pnmtosir pamtotga pnmtoxwd \
+		pnmtosgi pnmtosir pamtotga pnmtoxwd qoitopam \
 		rasttopnm rlatopam sgitopnm sirtopnm srftopam sunicontopnm \
-		winicontopam xwdtopnm yuy2topam zeisstopnm
+		winicontopam xwdtopnm yuy2topam zeisstopnm \
 
 ifneq ($(DONT_HAVE_PROCESS_MGMT),Y)
   PORTBINARIES += pstopnm pnmtops
@@ -168,7 +169,7 @@ BINARIES = $(PORTBINARIES)
 
 MERGEBINARIES = $(BINARIES)
 
-EXTRA_OBJECTS = exif.o rast.o ipdb.o srf.o
+EXTRA_OBJECTS = exif.o rast.o ipdb.o srf.o qoi.o
 ifeq ($(HAVE_PNGLIB),Y)
   EXTRA_OBJECTS += pngtxt.o
   EXTRA_OBJECTS += pngx.o
@@ -238,6 +239,11 @@ jpegtopnm: jpegdatasource.o exif.o
 jpegtopnm: ADDL_OBJECTS = jpegdatasource.o exif.o
 jpegtopnm: LDFLAGS_TARGET = $(shell $(LIBOPT) $(LIBOPTR) $(JPEGLIB))
 
+pamtoqoi: pamtoqoi.o qoi.o
+pamtoqoi: ADDL_OBJECTS = qoi.o
+qoitopam: pamtoqoi.o qoi.o
+qoitopam: ADDL_OBJECTS = qoi.o
+
 srftopam pamtosrf: srf.o
 srftopam pamtosrf: ADDL_OBJECTS = srf.o
 
diff --git a/converter/other/pamtoqoi.c b/converter/other/pamtoqoi.c
new file mode 100644
index 00000000..9f8e001b
--- /dev/null
+++ b/converter/other/pamtoqoi.c
@@ -0,0 +1,153 @@
+/*
+ * This file is part of Netpbm (http://netpbm.sourceforge.org).
+ * Copyright (c) 2022 cancername.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#include "pam.h"
+#include <string.h>
+#include <assert.h>
+#include "qoi.h"
+
+#define QOI_MAXVAL 0xFF
+
+/* tuple row to qoi row */
+typedef void (*trqr_t)(const tuplen *tuprow,
+                       size_t len,
+                       unsigned char *qoi_row);
+
+static void trqr_ppm(const tuplen *tuprow,
+               size_t len,
+               unsigned char *qoi_row) {
+    size_t j = 0;
+    for(size_t i = 0; i < len; i++) {
+        qoi_row[j++] = tuprow[i][0] * QOI_MAXVAL;
+        qoi_row[j++] = tuprow[i][1] * QOI_MAXVAL;
+        qoi_row[j++] = tuprow[i][2] * QOI_MAXVAL;
+    }
+}
+static void trqr_ppma(const tuplen *tuprow,
+               size_t len,
+               unsigned char *qoi_row) {
+    size_t j = 0;
+    for(size_t i = 0; i < len; i++) {
+        qoi_row[j++] = tuprow[i][0] * QOI_MAXVAL;
+        qoi_row[j++] = tuprow[i][1] * QOI_MAXVAL;
+        qoi_row[j++] = tuprow[i][2] * QOI_MAXVAL;
+        qoi_row[j++] = tuprow[i][3] * QOI_MAXVAL;
+    }
+}
+
+static void trqr_pgm(const tuplen *tuprow,
+               size_t len,
+               unsigned char *qoi_row) {
+    size_t j = 0;
+    for(size_t i = 0; i < len; i++) {
+        unsigned char tmp = tuprow[i][0] * QOI_MAXVAL;
+        qoi_row[j++] = tmp;
+        qoi_row[j++] = tmp;
+        qoi_row[j++] = tmp;
+    }
+}
+static void trqr_pgma(const tuplen *tuprow,
+               size_t len,
+               unsigned char *qoi_row) {
+    size_t j = 0;
+    for(size_t i = 0; i < len; i++) {
+        unsigned char tmp = tuprow[i][0] * QOI_MAXVAL;
+        qoi_row[j++] = tmp;
+        qoi_row[j++] = tmp;
+        qoi_row[j++] = tmp;
+        qoi_row[j++] = tuprow[i][1] * QOI_MAXVAL;
+    }
+}
+
+static trqr_t get_trqr(const char *tuple_type) {
+
+    if(!strcmp(tuple_type, PAM_PPM_TUPLETYPE))
+       return trqr_ppm;
+
+    if(!strcmp(tuple_type, PAM_PPM_ALPHA_TUPLETYPE))
+        return trqr_ppma;
+
+    if(!strcmp(tuple_type, PAM_PBM_TUPLETYPE) ||
+       !strcmp(tuple_type, PAM_PGM_TUPLETYPE))
+        return trqr_pgm;
+
+    if(!strcmp(tuple_type, PAM_PBM_ALPHA_TUPLETYPE) ||
+       !strcmp(tuple_type, PAM_PGM_ALPHA_TUPLETYPE))
+        return trqr_pgma;
+    return NULL;
+}
+
+int main(int argc, char **argv) {
+    struct pam input;
+    trqr_t trqr = NULL;
+    qoi_desc qd = {
+        .colorspace = QOI_SRGB
+    };
+    tuplen *tr = NULL;
+    unsigned char *qb = NULL;
+
+    pm_proginit(&argc, (const char **)argv);
+
+    pnm_readpaminit(stdin, &input, PAM_STRUCT_SIZE(tuple_type));
+    tr = pnm_allocpamrown(&input);
+
+    qd.width = input.width;
+    qd.height = input.height;
+    qd.channels = input.depth <= 3 ? 3 : 4;
+
+    qb = malloc(qd.width * qd.height * qd.channels);
+
+    trqr = get_trqr(input.tuple_type);
+    if(!trqr) {
+        pm_message("Unknown tuple type. Determining conversion by depth.");
+        switch(input.depth) {
+            case 1:
+            trqr = trqr_pgm;
+            pm_message("Conversion: like grayscale");
+            break;
+
+            case 2:
+            trqr = trqr_pgma;
+            pm_message("Conversion: like grayscale_alpha");
+            break;
+
+            case 3:
+            trqr = trqr_ppm;
+            pm_message("Conversion: like rgb");
+            break;
+
+            case 4:
+            trqr = trqr_ppma;
+            pm_message("Conversion: like rgb_alpha");
+            break;
+
+            default:
+            pm_error("Unsupported depth?");
+            break;
+        }
+    }
+    /* Read and convert rows. */
+    for(size_t i = 0; i < qd.height; i++) {
+        pnm_readpamrown(&input, tr);
+        trqr(tr, input.width, qb + i * input.width * qd.channels);
+    }
+    pnm_freepamrown(tr);
+    int ol = 0;
+    unsigned char *buf = qoi_encode(qb, &qd, &ol);
+    free(qb);
+    fwrite(buf, ol, 1, stdout);
+    return 0;
+}
diff --git a/converter/other/qoi.c b/converter/other/qoi.c
new file mode 100644
index 00000000..d5962fc4
--- /dev/null
+++ b/converter/other/qoi.c
@@ -0,0 +1,2 @@
+#define QOI_IMPLEMENTATION
+#include "qoi.h"
diff --git a/converter/other/qoi.h b/converter/other/qoi.h
new file mode 100644
index 00000000..2b782860
--- /dev/null
+++ b/converter/other/qoi.h
@@ -0,0 +1,669 @@
+/*
+
+QOI - The "Quite OK Image" format for fast, lossless image compression
+
+Dominic Szablewski - https://phoboslab.org
+
+
+-- LICENSE: The MIT License(MIT)
+
+Copyright(c) 2021 Dominic Szablewski
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files(the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and / or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions :
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+
+-- 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 */
diff --git a/converter/other/qoitopam.c b/converter/other/qoitopam.c
new file mode 100644
index 00000000..f17f4609
--- /dev/null
+++ b/converter/other/qoitopam.c
@@ -0,0 +1,148 @@
+/*
+ * This file is part of Netpbm (http://netpbm.sourceforge.org).
+ * Copyright (c) 2022 cancername.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#include "pam.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <malloc.h>
+#include <string.h>
+#include "qoi.h"
+
+#define QOI_MAXVAL 0xFF
+
+/* Resizes buf of type T* so that at least needed+1 bytes
+   are available, executing err if realloc fails.
+   Uses realloc -- is there a Netpbm equivalent? */
+#define RESIZE(buf, T, needed, allocated, err)  \
+    do {                                        \
+    size_t tmpn = (allocated);                  \
+    while((needed)+1 >= tmpn)                   \
+        tmpn = tmpn ? tmpn * 2 : 8;             \
+    if(tmpn != allocated) {                     \
+        T *tmpb = realloc((buf), tmpn);         \
+        if(!tmpb) {err}                         \
+        else {                                  \
+            (allocated) = tmpn;                 \
+            (buf) = tmpb;                       \
+        }                                       \
+    }                                           \
+    } while(0)
+
+
+/* Unfortunately, qoi.h does not implement a streaming decoder,
+   we need to read the whole stream into memory -- expensive.
+   We might be able to cheat here with mmap sometimes,
+   but it's not worth the effort. */
+static void *read_into_mem(FILE *f, size_t *s) {
+    *s = 0;
+    unsigned char *buf = NULL;
+    size_t allocated = 0;
+    size_t x = 0;
+    size_t r = 0;
+
+    do {
+        x += r;
+        RESIZE(buf, unsigned char, x+4096, allocated, free(buf); return NULL;);
+        r = fread(buf + x, 1, 4096, f);
+    } while(r != 0);
+
+    if(ferror(f)) {
+        free(buf);
+        return NULL;
+    }
+    else {
+        /* buf = realloc(buf, x); */
+        *s = x;
+        return buf;
+    }
+}
+
+int main(int argc, char **argv) {
+    struct pam output = {
+        .size = sizeof(struct pam),
+        .len = PAM_STRUCT_SIZE(tuple_type),
+        .maxval = QOI_MAXVAL,
+        .plainformat = 0
+    };
+
+    qoi_desc qd = {
+        .channels = 0
+    };
+
+    pm_proginit(&argc, (const char **)argv);
+
+    size_t il = 0;
+    char *img;
+    unsigned char *qoi_buf;
+    tuple *tr;
+
+    img = read_into_mem(stdin, &il);
+
+    if(!img || il == 0)
+        pm_error("Failed to read qoi into memory.");
+
+    qoi_buf = qoi_decode(img, il, &qd, 0);
+    free(img);
+
+    if(!qoi_buf)
+        pm_error("Decoding qoi failed.");
+
+    output.depth = qd.channels == 3 ? 3 : 4;
+    output.width = qd.width;
+    output.height = qd.height;
+    output.file = stdout;
+
+    /* Output PPM if the input is RGB only,
+       PAM with tuple type RGB_ALPHA otherwise. */
+    if(qd.channels == 3) {
+        output.format = PPM_FORMAT;
+        strcpy(output.tuple_type, PAM_PPM_TUPLETYPE);
+    }
+    else {
+        output.format = PAM_FORMAT;
+        strcpy(output.tuple_type, PAM_PPM_ALPHA_TUPLETYPE);
+    }
+    pnm_writepaminit(&output);
+    tr = pnm_allocpamrow(&output);
+
+    size_t k = 0;
+
+    if(output.depth == 3) {
+        for(int i = 0; i < output.height; i++) {
+            for(int j = 0; j < output.width; j++) {
+                tr[j][0] = qoi_buf[k++];
+                tr[j][1] = qoi_buf[k++];
+                tr[j][2] = qoi_buf[k++];
+            }
+            pnm_writepamrow(&output, tr);
+        }
+    }
+    else {
+        for(int i = 0; i < output.height; i++) {
+            for(int j = 0; j < output.width; j++) {
+                tr[j][0] = qoi_buf[k++];
+                tr[j][1] = qoi_buf[k++];
+                tr[j][2] = qoi_buf[k++];
+                tr[j][3] = qoi_buf[k++];
+            }
+            pnm_writepamrow(&output, tr);
+        }
+    }
+
+    free(qoi_buf);
+    pnm_freepamrow(tr);
+    return 0;
+}