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#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <arpa/inet.h>
#define STB_IMAGE_IMPLEMENTATION
#include <stb_image.h>
#include <memory>
static const int IMAGE_EDGE_PX = 64;
static const int PIXEL_DEPTH_BYTES = 2;
static const int PACKED_FRAME_SIZE_BYTES =
IMAGE_EDGE_PX * IMAGE_EDGE_PX * PIXEL_DEPTH_BYTES;
using ManagedPointer = std::unique_ptr<unsigned char[], decltype(std::free) *>;
ManagedPointer load_image(const char *path, int *w, int *h, int *channels) {
unsigned char *image_data = stbi_load(path, w, h, channels, 3);
return ManagedPointer(image_data, std::free);
}
ManagedPointer pack_image_565(unsigned char *rgb_data, int channels) {
uint16_t *data = static_cast<uint16_t *>(
calloc(IMAGE_EDGE_PX * IMAGE_EDGE_PX * PIXEL_DEPTH_BYTES, 1));
// To get as much data in there as we can, just pack it as RGB 565
for (int i = 0; i < IMAGE_EDGE_PX * IMAGE_EDGE_PX; i++) {
uint8_t r, g, b;
// Handle possibility of alpha
if (channels == 4) {
// RGBA data
// Just scale the RGB channels by the alpha channel (as though it were
// alpha over a black background)
uint8_t a = rgb_data[i * 4 + 2];
const float alpha_scale = ((float)a) / 255.0;
r = ((float)rgb_data[i * 4]) * alpha_scale;
g = ((float)rgb_data[i * 4 + 1]) * alpha_scale;
b = ((float)rgb_data[i * 4 + 2]) * alpha_scale;
} else {
// Straight up RGB
r = rgb_data[i * 3];
g = rgb_data[i * 3 + 1];
b = rgb_data[i * 3 + 2];
}
// Pack it into the output data
data[i] = htons((((r >> 3) & 0b11111) << 11) |
(((g >> 2) & 0b111111) << 5) | (((b >> 3) & 0b11111) << 0));
}
return ManagedPointer(reinterpret_cast<unsigned char *>(data), std::free);
}
int main(int argc, char **argv) {
if (argc < 3) {
fprintf(stderr, "%s output_file input_image_1 [input_image_2,...]\n",
argv[0]);
return EXIT_FAILURE;
}
// Create/open output file
int output_fd = ::open(argv[1], O_WRONLY | O_CREAT, 0644);
if (output_fd == -1) {
fprintf(stderr, "Failed to open '%s' for writing: %d: %s\n", argv[1], errno,
strerror(errno));
return EXIT_FAILURE;
}
// Close the file when done
std::shared_ptr<void> _defer_close_fd(nullptr, [=](...) {
int ret = close(output_fd);
if (ret == -1) {
fprintf(stderr, "Error closing output fd: %d: %s\n", errno,
strerror(errno));
}
});
for (int img_idx = 2; img_idx < argc; img_idx++) {
// Load the image
int width, height, channels;
ManagedPointer img = load_image(argv[img_idx], &width, &height, &channels);
// Don't bother with images that are the wrong dimension
if (width != IMAGE_EDGE_PX || height != IMAGE_EDGE_PX) {
fprintf(stderr, "Error: File '%s' is %dx%d, not %dx%d\n", argv[img_idx],
width, height, IMAGE_EDGE_PX, IMAGE_EDGE_PX);
return EXIT_FAILURE;
}
fprintf(stderr, "%s: %d channels\n", argv[img_idx], channels);
// Pack it to an animation frame
ManagedPointer packed = pack_image_565(img.get(), channels);
// Write those bytes to the output file
write(output_fd, packed.get(), PACKED_FRAME_SIZE_BYTES);
}
}