Add test1

makefile

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+TARGETS=test1
+OUTPUTS=$(addsuffix .png, $(TARGETS))
+
+all: $(TARGETS)
+test: $(TARGETS) $(OUTPUTS)
+
+%.: %.c
+	gcc -Wall -O3 -o $@ $<
+
+%.png: %
+	time ./$<
+
+clean:
+	rm $(TARGETS) *.png

svpng.inc

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+/*
+Copyright (C) 2017 Milo Yip. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+
+* Neither the name of pngout nor the names of its
+  contributors may be used to endorse or promote products derived from
+  this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+/*! \file
+    \brief      svpng() is a minimalistic C function for saving RGB/RGBA image into uncompressed PNG.
+    \author     Milo Yip
+    \version    0.1.1
+    \copyright  MIT license
+    \sa         http://github.com/miloyip/svpng
+*/
+
+#ifndef SVPNG_INC_
+#define SVPNG_INC_
+
+/*! \def SVPNG_LINKAGE
+    \brief User customizable linkage for svpng() function.
+    By default this macro is empty.
+    User may define this macro as static for static linkage, 
+    and/or inline in C99/C++, etc.
+*/
+#ifndef SVPNG_LINKAGE
+#define SVPNG_LINKAGE
+#endif
+
+/*! \def SVPNG_OUTPUT
+    \brief User customizable output stream.
+    By default, it uses C file descriptor and fputc() to output bytes.
+    In C++, for example, user may use std::ostream or std::vector instead.
+*/
+#ifndef SVPNG_OUTPUT
+#include <stdio.h>
+#define SVPNG_OUTPUT FILE* fp
+#endif
+
+/*! \def SVPNG_PUT
+    \brief Write a byte
+*/
+#ifndef SVPNG_PUT
+#define SVPNG_PUT(u) fputc(u, fp)
+#endif
+
+
+/*!
+    \brief Save a RGB/RGBA image in PNG format.
+    \param SVPNG_OUTPUT Output stream (by default using file descriptor).
+    \param w Width of the image. (<16383)
+    \param h Height of the image.
+    \param img Image pixel data in 24-bit RGB or 32-bit RGBA format.
+    \param alpha Whether the image contains alpha channel.
+*/
+SVPNG_LINKAGE void svpng(SVPNG_OUTPUT, unsigned w, unsigned h, const unsigned char* img, int alpha) {
+    static const unsigned t[] = { 0, 0x1db71064, 0x3b6e20c8, 0x26d930ac, 0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c, 
+    /* CRC32 Table */    0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c, 0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c };
+    unsigned a = 1, b = 0, c, p = w * (alpha ? 4 : 3) + 1, x, y, i;   /* ADLER-a, ADLER-b, CRC, pitch */
+#define SVPNG_U8A(ua, l) for (i = 0; i < l; i++) SVPNG_PUT((ua)[i]);
+#define SVPNG_U32(u) do { SVPNG_PUT((u) >> 24); SVPNG_PUT(((u) >> 16) & 255); SVPNG_PUT(((u) >> 8) & 255); SVPNG_PUT((u) & 255); } while(0)
+#define SVPNG_U8C(u) do { SVPNG_PUT(u); c ^= (u); c = (c >> 4) ^ t[c & 15]; c = (c >> 4) ^ t[c & 15]; } while(0)
+#define SVPNG_U8AC(ua, l) for (i = 0; i < l; i++) SVPNG_U8C((ua)[i])
+#define SVPNG_U16LC(u) do { SVPNG_U8C((u) & 255); SVPNG_U8C(((u) >> 8) & 255); } while(0)
+#define SVPNG_U32C(u) do { SVPNG_U8C((u) >> 24); SVPNG_U8C(((u) >> 16) & 255); SVPNG_U8C(((u) >> 8) & 255); SVPNG_U8C((u) & 255); } while(0)
+#define SVPNG_U8ADLER(u) do { SVPNG_U8C(u); a = (a + (u)) % 65521; b = (b + a) % 65521; } while(0)
+#define SVPNG_BEGIN(s, l) do { SVPNG_U32(l); c = ~0U; SVPNG_U8AC(s, 4); } while(0)
+#define SVPNG_END() SVPNG_U32(~c)
+    SVPNG_U8A("\x89PNG\r\n\32\n", 8);           /* Magic */
+    SVPNG_BEGIN("IHDR", 13);                    /* IHDR chunk { */
+    SVPNG_U32C(w); SVPNG_U32C(h);               /*   Width & Height (8 bytes) */
+    SVPNG_U8C(8); SVPNG_U8C(alpha ? 6 : 2);     /*   Depth=8, Color=True color with/without alpha (2 bytes) */
+    SVPNG_U8AC("\0\0\0", 3);                    /*   Compression=Deflate, Filter=No, Interlace=No (3 bytes) */
+    SVPNG_END();                                /* } */
+    SVPNG_BEGIN("IDAT", 2 + h * (5 + p) + 4);   /* IDAT chunk { */
+    SVPNG_U8AC("\x78\1", 2);                    /*   Deflate block begin (2 bytes) */
+    for (y = 0; y < h; y++) {                   /*   Each horizontal line makes a block for simplicity */
+        SVPNG_U8C(y == h - 1);                  /*   1 for the last block, 0 for others (1 byte) */
+        SVPNG_U16LC(p); SVPNG_U16LC(~p);        /*   Size of block in little endian and its 1's complement (4 bytes) */
+        SVPNG_U8ADLER(0);                       /*   No filter prefix (1 byte) */
+        for (x = 0; x < p - 1; x++, img++)
+            SVPNG_U8ADLER(*img);                /*   Image pixel data */
+    }
+    SVPNG_U32C((b << 16) | a);                  /*   Deflate block end with adler (4 bytes) */
+    SVPNG_END();                                /* } */
+    SVPNG_BEGIN("IEND", 0); SVPNG_END();        /* IEND chunk {} */
+}
+
+#endif /* SVPNG_INC_ */

test1.c

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+#include "svpng.inc"
+#include <math.h> // fminf(), sinf(), cosf()
+#include <stdlib.h> // rand(), RAND_MAX
+
+#define TWO_PI 6.28318530718f
+#define W 512
+#define H 512
+#define N 64
+#define MAX_STEP 10
+#define MAX_DISTANCE 2.0f
+#define EPSILON 1e-6f
+
+unsigned char img[W * H * 3];
+
+float circleSDF(float x, float y, float cx, float cy, float r) {
+    float ux = x - cx, uy = y - cy;
+    return sqrtf(ux * ux + uy * uy) - r;
+}
+
+float trace(float ox, float oy, float dx, float dy) {
+    float t = 0.0f;
+    for (int i = 0; i < MAX_STEP && t < MAX_DISTANCE; i++) {
+        float sd = circleSDF(ox + dx * t, oy + dy * t, 0.5f, 0.5f, 0.1f);
+        if (sd < EPSILON)
+            return 2.0f;
+        t += sd;
+    }
+    return 0.0f;
+}
+
+float sample(float x, float y) {
+    float sum = 0.0f;
+    for (int i = 0; i < N; i++) {
+        // float a = TWO_PI * rand() / RAND_MAX;
+        // float a = TWO_PI * i / N;
+        float a = TWO_PI * (i + (float)rand() / RAND_MAX) / N;
+        sum += trace(x, y, cosf(a), sinf(a));
+    }
+    return sum / N;
+}
+
+int main() {
+    unsigned char* p = img;
+    for (int y = 0; y < H; y++)
+        for (int x = 0; x < W; x++, p += 3)
+            p[0] = p[1] = p[2] = (int)(fminf(sample((float)x / W, (float)y / H) * 255.0f, 255.0f));
+    svpng(fopen("test1.png", "wb"), W, H, img, 0);
+}