diff --git a/libfprint/fpi-img-pixman.c b/libfprint/fpi-img-pixman.c
index 4704461..1c1bedb 100644
--- a/libfprint/fpi-img-pixman.c
+++ b/libfprint/fpi-img-pixman.c
@@ -23,6 +23,18 @@
 
 #include "fp_internal.h"
 
+/**
+ * fpi_img_resize:
+ * @img: an #fp_img image
+ * @w_factor: horizontal factor to resize the image by
+ * @h_factor: vertical factor to resize the image by
+ *
+ * Resizes the #fp_img image by scaling it by @w_factor times horizontally
+ * and @h_factor times vertically.
+ *
+ * Returns: a newly allocated #fp_img, the original @img will not be modified
+ * and will also need to be freed
+ */
 struct fp_img *fpi_img_resize(struct fp_img *img, unsigned int w_factor, unsigned int h_factor)
 {
 	int new_width = img->width * w_factor;
diff --git a/libfprint/fpi-img.c b/libfprint/fpi-img.c
index 378dfd7..7b9354e 100644
--- a/libfprint/fpi-img.c
+++ b/libfprint/fpi-img.c
@@ -59,6 +59,15 @@
  * front-end applications.
  */
 
+/**
+ * fpi_img_new:
+ * @length: the length of data to allocate
+ *
+ * Creates a new #fp_img structure with @length bytes of data allocated
+ * to hold the image.
+ *
+ * Returns: a new #fp_img to free with fp_img_free()
+ */
 struct fp_img *fpi_img_new(size_t length)
 {
 	struct fp_img *img = g_malloc0(sizeof(*img) + length);
@@ -67,6 +76,16 @@ struct fp_img *fpi_img_new(size_t length)
 	return img;
 }
 
+/**
+ * fpi_img_new_for_imgdev:
+ * @imgdev: a #fp_img_dev imaging fingerprint device
+ *
+ * Creates a new #fp_img structure, like fpi_img_new(), but uses the
+ * driver's advertised height and width to calculate the size of the
+ * length of data to allocate.
+ *
+ * Returns: a new #fp_img to free with fp_img_free()
+ */
 struct fp_img *fpi_img_new_for_imgdev(struct fp_img_dev *imgdev)
 {
 	struct fp_img_driver *imgdrv = fpi_driver_to_img_driver(FP_DEV(imgdev)->drv);
@@ -78,6 +97,16 @@ struct fp_img *fpi_img_new_for_imgdev(struct fp_img_dev *imgdev)
 	return img;
 }
 
+/**
+ * fpi_img_is_sane:
+ * @img: a #fp_img image
+ *
+ * Checks whether an #fp_img structure passes some basic checks, such
+ * as length, width and height being non-zero, and the buffer being
+ * big enough to hold the image of said size.
+ *
+ * Returns: %TRUE if the image is sane, %FALSE otherwise
+ */
 gboolean fpi_img_is_sane(struct fp_img *img)
 {
 	guint len;
@@ -98,6 +127,15 @@ gboolean fpi_img_is_sane(struct fp_img *img)
 	return TRUE;
 }
 
+/**
+ * fpi_img_realloc:
+ * @img: an #fp_img image
+ * @newsize: the new length of the image
+ *
+ * Changes the size of the data part of the #fp_img.
+ *
+ * Returns: the modified #fp_img, the same as the first argument to this function
+ */
 struct fp_img *fpi_img_realloc(struct fp_img *img, size_t newsize)
 {
 	return g_realloc(img, sizeof(*img) + newsize);
diff --git a/libfprint/fpi-img.h b/libfprint/fpi-img.h
index 580c41a..ab4bfe8 100644
--- a/libfprint/fpi-img.h
+++ b/libfprint/fpi-img.h
@@ -47,6 +47,21 @@ typedef enum {
 	FP_IMG_PARTIAL         = 1 << 4
 } FpiImgFlags;
 
+/**
+ * fp_img:
+ * @width: the width of the image
+ * @height: the height of the image
+ * @length: the length of the data associated with the image
+ * @flags: @FpiImgFlags flags describing the image contained in the structure
+ * @minutiae: an opaque structure representing the detected minutiae
+ * @binarized: the binarized image data
+ * @data: the start of the image data, which will be of @length size.
+ *
+ * A structure representing a captured, or processed image. The @flags member
+ * will show its current state, including whether whether the binarized form
+ * if present, whether it is complete, and whether it needs particular changes
+ * before being processed.
+ */
 struct fp_img {
 	int width;
 	int height;
@@ -58,7 +73,7 @@ struct fp_img {
 };
 
 struct fp_img *fpi_img_new(size_t length);
-struct fp_img *fpi_img_new_for_imgdev(struct fp_img_dev *dev);
+struct fp_img *fpi_img_new_for_imgdev(struct fp_img_dev *imgdev);
 struct fp_img *fpi_img_realloc(struct fp_img *img, size_t newsize);
 struct fp_img *fpi_img_resize(struct fp_img *img, unsigned int w_factor, unsigned int h_factor);