Image standardization

Initially supports flipping and colour inversion

examples/img_capture.c

@@ -92,6 +92,13 @@ int main(void)
 		goto out_close;
 	}
 
+	fp_img_standardize(img);
+	r = fp_img_save_to_file(img, "finger_standardized.pgm");
+	if (r) {
+		fprintf(stderr, "standardized img save failed, code %d\n", r);
+		goto out_close;
+	}
+
 	r = 0;
 out_close:
 	fp_dev_close(dev);

libfprint/drivers/uru4000.c

@@ -294,6 +294,7 @@ static int capture(struct fp_img_dev *dev, gboolean unconditional,
 	img = fpi_img_resize(img, image_size);
 	img->width = IMG_WIDTH;
 	img->height = IMG_HEIGHT;
+	img->flags = FP_IMG_V_FLIPPED | FP_IMG_H_FLIPPED | FP_IMG_COLORS_INVERTED;
 
 	*ret = img;
 	return 0;

libfprint/fp_internal.h

@@ -155,10 +155,16 @@ struct fp_print_data {
 struct fp_print_data *fpi_print_data_new(struct fp_dev *dev, size_t length);
 int fpi_print_data_compatible(struct fp_dev *dev, struct fp_print_data *data);
 
+/* bit values for fp_img.flags */
+#define FP_IMG_V_FLIPPED 		(1<<0)
+#define FP_IMG_H_FLIPPED 		(1<<1)
+#define FP_IMG_COLORS_INVERTED	(1<<2)
+
 struct fp_img {
 	int width;
 	int height;
 	size_t length;
+	uint16_t flags;
 	unsigned char data[0];
 };
 

libfprint/fprint.h

@@ -97,6 +97,7 @@ int fp_img_get_height(struct fp_img *img);
 int fp_img_get_width(struct fp_img *img);
 unsigned char *fp_img_get_data(struct fp_img *img);
 int fp_img_save_to_file(struct fp_img *img, char *path);
+void fp_img_standardize(struct fp_img *img);
 
 /* Library */
 int fp_init(void);

libfprint/img.c

@@ -104,3 +104,63 @@ API_EXPORTED int fp_img_save_to_file(struct fp_img *img, char *path)
 	return 0;
 }
 
+static void vflip(struct fp_img *img)
+{
+	int width = img->width;
+	int data_len = img->width * img->height;
+	unsigned char rowbuf[width];
+	int i;
+
+	for (i = 0; i < img->height / 2; i++) {
+		int offset = i * width;
+		int swap_offset = data_len - (width * (i + 1));
+
+		/* copy top row into buffer */
+		memcpy(rowbuf, img->data + offset, width);
+
+		/* copy lower row over upper row */
+		memcpy(img->data + offset, img->data + swap_offset, width);
+
+		/* copy buffer over lower row */
+		memcpy(img->data + swap_offset, rowbuf, width);
+	}
+}
+
+static void hflip(struct fp_img *img)
+{
+	int width = img->width;
+	unsigned char rowbuf[width];
+	int i, j;
+
+	for (i = 0; i < img->height; i++) {
+		int offset = i * width;
+
+		memcpy(rowbuf, img->data + offset, width);
+		for (j = 0; j < width; j++)
+			img->data[offset + j] = rowbuf[width - j - 1];
+	}
+}
+
+static void invert_colors(struct fp_img *img)
+{
+	int data_len = img->width * img->height;
+	int i;
+	for (i = 0; i < data_len; i++)
+		img->data[i] = 0xff - img->data[i];
+}
+
+API_EXPORTED void fp_img_standardize(struct fp_img *img)
+{
+	if (img->flags & FP_IMG_V_FLIPPED) {
+		vflip(img);
+		img->flags &= ~FP_IMG_V_FLIPPED;
+	}
+	if (img->flags & FP_IMG_H_FLIPPED) {
+		hflip(img);
+		img->flags &= ~FP_IMG_H_FLIPPED;
+	}
+	if (img->flags & FP_IMG_COLORS_INVERTED) {
+		invert_colors(img);
+		img->flags &= ~FP_IMG_COLORS_INVERTED;
+	}
+}