Kobo Screen captute via HTTP

fb2bmp.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

struct __attribute__((packed)) bitmapFileHeader {
	unsigned char	bfType[2];
	unsigned int	bfSize;
	unsigned short	bfReserved1;
	unsigned short	bfReserved2;
	unsigned int	bfOffBits;
};

struct __attribute__((packed)) bitmapInfoHeader {
	unsigned int	biSize;
	unsigned int	biWidth;
	unsigned int	biHeight;
	unsigned short	biPlanes;
	unsigned short	biBitCount;
	unsigned int	biCompression;
	unsigned int	biSizeImage;
	unsigned int	biXPixPerMeter;
	unsigned int	biYPixPerMeter;
	unsigned int	biClrUsed;
	unsigned int	biCirImportant;
};

static unsigned short pix565[600][800];

int main(void)
{
	unsigned int w = 600, h = 800, x, y;
	int fhsize = sizeof(struct bitmapFileHeader);
	int ihsize = sizeof(struct bitmapInfoHeader);
	struct bitmapFileHeader fileHeader =
		{"BM", fhsize+ihsize+w*h*3, 0, 0, fhsize+ihsize};
	struct bitmapInfoHeader infoHeader =
		{ihsize, w, h, 1, 24, 0, w*h*3, 0, 0, 0, 0};
	int fd, ret;

	fd = open("/dev/fb0", O_RDONLY);
	ret = read(fd, pix565, sizeof(pix565));
	if (ret < 0) {
		perror("read error");
		exit(0);
	}

	puts("HTTP/1.0 200 OK");
	puts("Content-Type: image/bmp");
	puts("");

	fwrite(&fileHeader, sizeof(fileHeader), 1, stdout);
	fwrite(&infoHeader, sizeof(infoHeader), 1, stdout);

	for (y = 0; y < h; y++) for (x = 0; x < w; x++) {
		unsigned short val = pix565[w-x-1][h-y-1]; // rotated
		unsigned short r5 = (val>>11) & 0x1F; // 5 bits
		unsigned short g6 = (val>> 5) & 0x3F; // 6 bits
		unsigned short b5 = (val    ) & 0x1F; // 5 bits

		printf("%c%c%c",
			(b5<<3)+(b5>>2), (g6<<2)+(g6>>4), (r5<<3)+(r5>>2));
	}
	return 0;
}

inetd.conf

# <service_name> <sock_type> <proto> <flags> <user> <server_path> <args>
21      stream  tcp     nowait  root    /bin/busybox ftpd -w -S /
23      stream  tcp     nowait  root    /bin/busybox telnetd -i
80      stream  tcp     nowait  root    /usr/bin/fb2bmp