Implement working with image bytes directly (no file required). (#88)

* Implement working with image bytes directly (no file required).

Co-authored-by: Matthew Tamayo <matthew@getmethodic.com>

* fix: `covert` to `convert`

* fix: un-`pub` new conversion function, improve documentation

* fix: broken doc link

---------

Co-authored-by: geekbeast <geekbeast@users.noreply.github.com>
Co-authored-by: Matthew Tamayo <matthew@getmethodic.com>
Co-authored-by: Andrew Brown <andrew.brown@intel.com>

image2tensor/src/lib.rs

@@ -14,10 +14,10 @@ pub enum ColorOrder {
     BGR,
 }
 
-// Take the image located at 'path', open it, resize it to height x width, and then converts
-// the pixel precision to the type requested. NOTE: this function assumes the image is in
-// standard 8bit RGB format. It should work with standard image formats such as .jpg, .png, etc
-pub fn convert_image_to_bytes(
+// Take the image located at 'path', open it, resize it to `height` x `width`, and then convert the
+// pixel precision to the type requested. NOTE: this function assumes the image is in standard 8-bit
+// RGB format. It should work with standard image formats such as `.jpg`, `.png`, etc.
+pub fn convert_image_to_tensor_bytes(
     path: &str,
     width: u32,
     height: u32,
@@ -35,8 +35,32 @@ pub fn convert_image_to_bytes(
         .map_err(|_| format!("Failed to decode the file: {:?}", path))
         .unwrap();
 
+    convert_dynamic_image_to_tensor_bytes(decoded, width, height, precision, order)
+}
+
+/// Same as [convert_image_to_tensor_bytes] but accepts a `bytes` slice instead.
+pub fn convert_image_bytes_to_tensor_bytes(
+    bytes: &[u8],
+    width: u32,
+    height: u32,
+    precision: TensorType,
+    order: ColorOrder,
+) -> Result<Vec<u8>, String> {
+    // Create the DynamicImage by decoding the image.
+    let decoded = image::load_from_memory(bytes).expect("Unable to load image from bytes.");
+
+    convert_dynamic_image_to_tensor_bytes(decoded, width, height, precision, order)
+}
+
+fn convert_dynamic_image_to_tensor_bytes(
+    image: DynamicImage,
+    width: u32,
+    height: u32,
+    precision: TensorType,
+    order: ColorOrder,
+) -> Result<Vec<u8>, String> {
     // Resize the image to the specified W/H and get an array of u8 RGB values.
-    let dyn_img: DynamicImage = decoded.resize_exact(width, height, image::imageops::Triangle);
+    let dyn_img: DynamicImage = image.resize_exact(width, height, image::imageops::Triangle);
     let mut img_bytes = dyn_img.into_bytes();
 
     // Get an array of the pixel values and return it.
@@ -46,13 +70,15 @@ pub fn convert_image_to_bytes(
     }
 }
 
+/// Calculate the expected tensor data size of an image of `width` x `height` with the given
+/// `precision`.
 pub fn calculate_buffer_size(width: u32, height: u32, precision: TensorType) -> usize {
     let bytes_per_pixel = get_bytes_per_pixel(precision);
     let pixels: u32 = width * height * 3;
     pixels as usize * bytes_per_pixel
 }
 
-// Save the bytes into the specified TensorType format.
+/// Save the bytes into the specified TensorType format.
 fn save_bytes(buffer: &[u8], tt: TensorType) -> Vec<u8> {
     let mut out: Vec<u8> = vec![];
 
@@ -80,7 +106,7 @@ fn get_bytes_per_pixel(precision: TensorType) -> usize {
     }
 }
 
-// Converts an RGB array to BGR
+/// Converts an RGB array to BGR.
 fn rgb_to_bgr(buffer: &mut [u8]) -> &[u8] {
     for i in (0..buffer.len()).step_by(3) {
         buffer.swap(i + 2, i);