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This commit is contained in:
Eggert Jung
2025-12-17 02:00:39 +01:00
parent 6c4da20268
commit 97e9a03610
5 changed files with 21 additions and 0 deletions
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21
img2wfm/makefile Normal file
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CC := gcc
CFLAGS := -Wall -Wextra -std=c11
LDLIBS := -lSDL2 -lSDL2_image
TARGET := waveform
SRC := waveform.c
# -------------------------------------------------
# Default target – just type `make` to build
all: $(TARGET)
# How to build the executable
$(TARGET): $(SRC)
$(CC) $(CFLAGS) $^ $(LDLIBS) -o $@
# Convenience: `make clean` to remove the binary
clean:
rm -f $(TARGET)
.PHONY: all clean

321
img2wfm/waveform.c Normal file
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/* -------------------------------------------------------------
* waveform_tcp.c
*
* * 600×400 ARGB8888 frame is streamed over a single‑client TCP socket.
* * The received frame is transformed so that the resulting bitmap
* can be displayed on a video waveform monitor and will look like
* the original picture.
*
* Build (Linux/macOS):
* gcc -Wall -Wextra -pedantic -std=c11 waveform_tcp.c \
* -lSDL2 -lpthread -o waveform_tcp
*
* Run:
* ./waveform_tcp # opens a window and listens on 0.0.0.0:12345
*
* Test client (Unix‑like, sends one frame of solid gray):
* dd if=/dev/zero bs=1 count=$((600*400*4)) | tr \\0 \\377 > gray.bin
* cat gray.bin | nc 127.0.0.1 12345
*
* ------------------------------------------------------------- */
#include <SDL2/SDL.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h> // memcpy, memset
#include <unistd.h> // close, read, write
#include <fcntl.h> // fcntl
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
/* -------------------------------------------------------------
* Configuration
* ------------------------------------------------------------- */
#define WIDTH 800
#define HEIGHT 600
#define LISTEN_PORT 12345 // change if you like
#define BACKLOG 1 // only one pending connection
/* -------------------------------------------------------------
* Simple pixel helpers (ARGB8888 – 0xAARRGGBB in memory)
* ------------------------------------------------------------- */
typedef Uint32 pixel_t;
static inline pixel_t make_pixel(Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
return (pixel_t)((a << 24) | (r << 16) | (g << 8) | b);
}
#define MAKE_OPAQUE_PIXEL(r,g,b) make_pixel((r),(g),(b),0xFF)
/* -------------------------------------------------------------
* Global buffers
* ------------------------------------------------------------- */
/* 1. The raw frame received from the network */
static pixel_t net_frame[HEIGHT][WIDTH];
/* 2. The image that we actually draw (after the waveform conversion) */
static pixel_t draw_buf[HEIGHT][WIDTH];
/* -------------------------------------------------------------
* Demo pattern – what we see until the first network frame arrives
* ------------------------------------------------------------- */
static void init_demo_pattern(void)
{
for (int y = 0; y < HEIGHT; ++y) {
for (int x = 0; x < WIDTH; ++x) {
Uint8 r = (HEIGHT-y)*255/HEIGHT;//(Uint8)((x * 255) / (WIDTH - 1));
Uint8 g = (HEIGHT-y)*255/HEIGHT;//(Uint8)((y * 255) / (HEIGHT - 1));
Uint8 b = (HEIGHT-y)*255/HEIGHT;//0x80;
draw_buf[y][x] = MAKE_OPAQUE_PIXEL(r, g, b);
}
}
}
/* -------------------------------------------------------------
* Luminance conversion – ITU‑BT.601 (Y = 0.299R + 0.587G + 0.114B)
* ------------------------------------------------------------- */
static inline Uint8 rgb_to_luma(Uint8 r, Uint8 g, Uint8 b)
{
/* weighted sum, integer arithmetic, rounded */
return (Uint8)((299 * r + 587 * g + 114 * b) / 1000);
}
/* -------------------------------------------------------------
* Transform the raw ARGB frame into a waveform‑ready image.
*
* * dest is the global draw_buf
* * every source pixel (sx, sy) becomes a white dot at
* dx = sx
* dy = round( luma * (HEIGHT‑1) / 255 )
*
* The whole destination buffer is cleared to black first.
* ------------------------------------------------------------- */
static void convert_to_waveform(void)
{
const pixel_t WHITE = 0xFFFFFFFFU; /* ARGB = opaque white */
const pixel_t BLACK = 0xFF000000U; /* opaque black (background) */
/* 1. clear destination */
for (int y = 0; y < HEIGHT; ++y)
memset(draw_buf[y], 0, WIDTH * sizeof(pixel_t));
for (int y = 0; y < HEIGHT; ++y)
for (int x = 0; x < WIDTH; ++x)
draw_buf[y][x] = BLACK;
/* 2. plot points */
for (int sy = 0; sy < HEIGHT; ++sy) {
for (int sx = 0; sx < WIDTH; ++sx) {
pixel_t p = net_frame[sy][sx];
Uint8 r = (Uint8)((p >> 16) & 0xFF);
Uint8 g = (Uint8)((p >> 8) & 0xFF);
Uint8 b = (Uint8)( p & 0xFF);
Uint8 luma = rgb_to_luma(r, g, b); /* 0‑255 */
if(luma >= 150)
draw_buf[sy][sx] = 0xff<<24 | (255-sy/2) << 16 | (255-sy/2) << 8 | (255-sy/2); /* overwrite – white dot */
else
draw_buf[sy][sx] = 0xff<<24;
//draw_buf[sy][sx] = (255-sy/2)<<24 | 0xFFFFFFU;
}
}
}
/* -------------------------------------------------------------
* ---------- TCP SERVER ------------------------------------
* ------------------------------------------------------------- */
/* Returns a non‑blocking listening socket, or -1 on error. */
static int create_listen_socket(void)
{
int lst = socket(AF_INET, SOCK_STREAM, 0);
if (lst < 0) {
perror("socket");
return -1;
}
int opt = 1;
setsockopt(lst, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
struct sockaddr_in addr = {
.sin_family = AF_INET,
.sin_port = htons(LISTEN_PORT),
.sin_addr = { .s_addr = INADDR_ANY }
};
if (bind(lst, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
perror("bind");
close(lst);
return -1;
}
if (listen(lst, BACKLOG) < 0) {
perror("listen");
close(lst);
return -1;
}
/* make non‑blocking */
int flags = fcntl(lst, F_GETFL, 0);
fcntl(lst, F_SETFL, flags | O_NONBLOCK);
printf("[net] Listening on 0.0.0.0:%d (single client allowed)\n", LISTEN_PORT);
return lst;
}
/* Helper – set a socket to non‑blocking mode */
static void set_nonblocking(int fd)
{
int flags = fcntl(fd, F_GETFL, 0);
if (flags != -1) fcntl(fd, F_SETFL, flags | O_NONBLOCK);
}
/* -------------------------------------------------------------
* MAIN
* ------------------------------------------------------------- */
int main(void)
{
/* ---------- SDL initialisation -------------------------------- */
if (SDL_Init(SDL_INIT_VIDEO) != 0) {
fprintf(stderr, "SDL_Init error: %s\n", SDL_GetError());
return EXIT_FAILURE;
}
SDL_Window *window = SDL_CreateWindow("Waveform‑ready demo (TCP input)",
SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED,
WIDTH, HEIGHT,
SDL_WINDOW_SHOWN);
if (!window) {
fprintf(stderr, "SDL_CreateWindow error: %s\n", SDL_GetError());
SDL_Quit();
return EXIT_FAILURE;
}
SDL_Renderer *renderer = SDL_CreateRenderer(window, -1,
SDL_RENDERER_ACCELERATED |
SDL_RENDERER_PRESENTVSYNC);
if (!renderer) {
fprintf(stderr, "SDL_CreateRenderer error: %s\n", SDL_GetError());
SDL_DestroyWindow(window);
SDL_Quit();
return EXIT_FAILURE;
}
SDL_Texture *texture = SDL_CreateTexture(renderer,
SDL_PIXELFORMAT_ARGB8888,
SDL_TEXTUREACCESS_STREAMING,
WIDTH, HEIGHT);
if (!texture) {
fprintf(stderr, "SDL_CreateTexture error: %s\n", SDL_GetError());
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
SDL_Quit();
return EXIT_FAILURE;
}
/* ---------- Demo pattern (until first network frame) ---------- */
init_demo_pattern();
/* ---------- Networking --------------------------------------- */
int listen_sock = create_listen_socket(); /* may be -1 on failure */
int client_sock = -1; /* -1 → no client yet */
const size_t FRAME_BYTES = WIDTH * HEIGHT * sizeof(pixel_t);
size_t recv_offset = 0; /* bytes already received */
bool quit = false;
SDL_Event ev;
/* ---------- Main loop --------------------------------------- */
while (!quit) {
/* 1) SDL events */
while (SDL_PollEvent(&ev)) {
if (ev.type == SDL_QUIT) quit = true;
else if (ev.type == SDL_KEYDOWN && ev.key.keysym.sym == SDLK_ESCAPE)
quit = true;
}
/* 2) Accept a new client if none is present */
if (listen_sock >= 0 && client_sock < 0) {
struct sockaddr_in remote;
socklen_t remote_len = sizeof(remote);
int tmp = accept(listen_sock,
(struct sockaddr *)&remote,
&remote_len);
if (tmp >= 0) {
client_sock = tmp;
set_nonblocking(client_sock);
recv_offset = 0;
char ip[INET_ADDRSTRLEN];
inet_ntop(AF_INET, &remote.sin_addr, ip, sizeof(ip));
printf("[net] Client connected from %s:%d\n", ip,
ntohs(remote.sin_port));
} else if (errno != EAGAIN && errno != EWOULDBLOCK) {
perror("[net] accept");
}
}
/* 3) Read raw pixel data from the client */
if (client_sock >= 0) {
size_t still_needed = FRAME_BYTES - recv_offset;
ssize_t n = recv(client_sock,
((Uint8 *)net_frame) + recv_offset,
still_needed,
0);
if (n > 0) {
recv_offset += (size_t)n;
if (recv_offset == FRAME_BYTES) {
/* Full frame received – convert to waveform image */
convert_to_waveform();
recv_offset = 0; /* ready for the next frame */
}
} else if (n == 0) {
printf("[net] Client disconnected.\n");
close(client_sock);
client_sock = -1;
} else if (n < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
perror("[net] recv");
close(client_sock);
client_sock = -1;
}
}
/* 4) Copy the (possibly transformed) draw buffer into the texture */
void *tex_pixels;
int tex_pitch;
if (SDL_LockTexture(texture, NULL, &tex_pixels, &tex_pitch) != 0) {
fprintf(stderr, "SDL_LockTexture error: %s\n", SDL_GetError());
break;
}
for (int y = 0; y < HEIGHT; ++y) {
memcpy((Uint8 *)tex_pixels + y * tex_pitch,
draw_buf[y],
WIDTH * sizeof(pixel_t));
}
SDL_UnlockTexture(texture);
/* 5) Render */
SDL_RenderClear(renderer);
SDL_RenderCopy(renderer, texture, NULL, NULL);
SDL_RenderPresent(renderer);
/* VSYNC caps the loop to the monitor refresh rate. */
}
/* -------------------------------------------------------------
* Cleanup
* ------------------------------------------------------------- */
if (client_sock >= 0) close(client_sock);
if (listen_sock >= 0) close(listen_sock);
SDL_DestroyTexture(texture);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
SDL_Quit();
return EXIT_SUCCESS;
}