blurrerbox

Makefile

@@ -0,0 +1,8 @@
+CFLAGS += -fopenmp $(shell pkg-config --cflags libjpeg) -g -fsanitize=address
+LDFLAGS += -fopenmp $(shell pkg-config --libs libjpeg) -fsanitize=address
+
+blurrerbox: blurrerbox.c
+
+.PHONY: clean
+clean:
+	rm -f blurrerbox

blurrerbox.c

@@ -0,0 +1,157 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <jpeglib.h>
+#include <omp.h>
+
+unsigned char *process_image(
+		unsigned char *input_image, int input_width, int input_height,
+		int desired_width, int desired_height) {
+	unsigned char *output = calloc(3, desired_width * desired_height);
+
+	double scale_w = (double)desired_width / (double)input_width;
+	double scale_h = (double)desired_height / (double)input_height;
+	double scale;
+	printf("scales are %fx%f\n", scale_w, scale_h);
+	int rect_x, rect_y, rect_w, rect_h;
+	if (scale_w < scale_h) {
+		printf("too wide?\n");
+		scale = scale_w;
+	} else {
+		printf("too tall?\n");
+		scale = scale_h;
+	}
+
+	rect_w = input_width * scale;
+	rect_h = input_height * scale;
+	rect_x = (desired_width - rect_w) / 2.0;
+	rect_y = (desired_height - rect_h) / 2.0;
+
+	printf("rect is %ix%i:%i,%i\n", rect_w, rect_h, rect_x, rect_y);
+
+	// Write main image
+#pragma omp parallel for
+	for (int y = 0; y < rect_h; ++y) {
+		for (int x = 0; x < rect_w; ++x) {
+			int input_y = y / scale;
+			int input_x = x / scale;
+			int input_idx = input_y * input_width * 3 + input_x * 3;
+			int output_idx = (y + rect_y) * desired_width * 3 + (x + rect_x) * 3;
+			output[output_idx + 0] = input_image[input_idx + 0];
+			output[output_idx + 1] = input_image[input_idx + 1];
+			output[output_idx + 2] = input_image[input_idx + 2];
+		}
+	}
+
+	return output;
+}
+
+unsigned char *read_jpg(FILE *in, int *width, int *height) {
+	struct jpeg_decompress_struct cinfo = { 0 };
+	struct jpeg_error_mgr jerr = { 0 };
+	cinfo.err = jpeg_std_error(&jerr);
+
+	jpeg_create_decompress(&cinfo);
+	jpeg_stdio_src(&cinfo, in);
+	jpeg_read_header(&cinfo, TRUE);
+	jpeg_start_decompress(&cinfo);
+
+	*width = cinfo.output_width;
+	*height = cinfo.output_height;
+	int bytes_per_line = cinfo.output_width * 3;
+	unsigned char *image = malloc(bytes_per_line * cinfo.output_height);
+
+	/* Make a one-row-high sample array that will go away when done with image */
+	JSAMPARRAY buffer = (*cinfo.mem->alloc_sarray)
+		((j_common_ptr)&cinfo, JPOOL_IMAGE, bytes_per_line, 1);
+
+	while (cinfo.output_scanline < cinfo.output_height) {
+		jpeg_read_scanlines(&cinfo, buffer, 1);
+			/* Assume put_scanline_someplace wants a pointer and sample count. */
+		memcpy(&image[bytes_per_line * (cinfo.output_scanline - 1)], buffer[0], bytes_per_line);
+	}
+
+	jpeg_finish_decompress(&cinfo);
+	jpeg_destroy_decompress(&cinfo);
+
+	return image;
+}
+
+void write_jpg(FILE *out, unsigned char *image, int width, int height) {
+	struct jpeg_compress_struct cinfo = { 0 };
+	struct jpeg_error_mgr jerr = { 0 };
+	cinfo.err = jpeg_std_error(&jerr);
+
+	jpeg_create_compress(&cinfo);
+	jpeg_stdio_dest(&cinfo, out);
+
+	printf("writing %ix%i\n", width, height);
+	cinfo.image_width = width;
+	cinfo.image_height = height;
+	cinfo.input_components = 3;
+	cinfo.in_color_space = JCS_RGB;
+
+	jpeg_set_defaults(&cinfo);
+	jpeg_set_quality(&cinfo, 90, FALSE);
+	jpeg_start_compress(&cinfo, TRUE);
+
+	int bytes_per_line = width * 3;
+	JSAMPROW row_pointer[1];
+
+	while (cinfo.next_scanline < cinfo.image_height) {
+		row_pointer[0] = &image[cinfo.next_scanline * bytes_per_line];
+		jpeg_write_scanlines(&cinfo, row_pointer, 1);
+	}
+
+	jpeg_finish_compress(&cinfo);
+	jpeg_destroy_compress(&cinfo);
+}
+
+int main(int argc, char **argv) {
+	if (argc != 4) {
+		printf("Usage: %s <resolution> <input> <output>\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	int desired_width, desired_height;
+	if (sscanf(argv[1], "%ix%i", &desired_width, &desired_height) != 2) {
+		fprintf(stderr, "Error parsing resolution '%s'\n", argv[1]);
+		return EXIT_FAILURE;
+	}
+
+	FILE *in;
+	if (strcmp(argv[2], "-") == 0) {
+		in = stdin;
+	} else {
+		in = fopen(argv[2], "r");
+		if (in == NULL) {
+			perror(argv[2]);
+			return EXIT_FAILURE;
+		}
+	}
+
+	int input_width, input_height;
+	unsigned char *input_image = read_jpg(in, &input_width, &input_height);
+	fclose(in);
+
+	unsigned char *output_image = process_image(
+			input_image, input_width, input_height, desired_width, desired_height);
+	free(input_image);
+
+	FILE *out;
+	if (strcmp(argv[3], "-") == 0) {
+		out = stdout;
+	} else {
+		out = fopen(argv[3], "w");
+		if (out == NULL) {
+			perror(argv[3]);
+			free(output_image);
+			return EXIT_FAILURE;
+		}
+	}
+
+	write_jpg(out, output_image, desired_width, desired_height);
+	free(output_image);
+
+	return EXIT_SUCCESS;
+}