Added watermark Rust example (#8)

* Added watermark Rust example * Addressed review comments * cleanup
G-Core · Dec 14, 2023 · 9206536 · 9206536
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diff --git a/fastedge-rust-sdk/examples/watermark/.cargo/config.toml b/fastedge-rust-sdk/examples/watermark/.cargo/config.toml
@@ -0,0 +1,2 @@
+[build]
+target = "wasm32-wasi"
diff --git a/fastedge-rust-sdk/examples/watermark/Cargo.toml b/fastedge-rust-sdk/examples/watermark/Cargo.toml
@@ -0,0 +1,17 @@
+[package]
+name = "watermark"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+fastedge = { path = "../../" }
+urlencoding = "2.1.2"
+url = "2.3.1"
+image = "0.24.5"
+rusty-s3 = "0.5.0"
+anyhow = "1.0.72"
+
+[lib]
+crate-type = ["cdylib"]
+
+[workspace]
diff --git a/fastedge-rust-sdk/examples/watermark/src/lib.rs b/fastedge-rust-sdk/examples/watermark/src/lib.rs
@@ -0,0 +1,236 @@
+// this example reads file from S3 storage, which must be confgiured for the app like this:
+//   "env": {
+//    "ACCESS_KEY": "<access_key>",
+//    "BASE_HOSTNAME": "<base_hostname>, e.g. cloud.gcore.lu",
+//    "BUCKET": "<bucket>",
+//    "REGION": "<region>",
+//    "SECRET_KEY": "<secret_key>"
+//  }
+// then apply watermark from file "sample.png", which is embedded during compilation process
+// and return resulting image as PNG.
+// if file from S3 cannot be recognised as valid image, it is passed to caller as is
+
+const DEFAULT_OPACITY: f32 = 1.0;   // to use non-default opacity, specify OPACITY in 0-1.0 range in app env
+
+use std::{
+    time::Duration,
+    env,
+    io::Cursor
+};
+use fastedge::{
+    body::Body,
+    http::{Error, header, Request, Response, StatusCode, Method}
+};
+use url::Url;
+use image::*;
+use rusty_s3::{Bucket, Credentials, S3Action, UrlStyle};
+
+#[fastedge::http]
+fn main(req: Request<Body>) -> Result<Response<Body>, Error> {
+    // embed watermark file - file must be present during compilation
+    let wm_buf = include_bytes!("sample.png");
+
+    // Filter request methods
+    match req.method() {
+        // Allow only GET and HEAD requests.
+        &Method::GET | &Method::HEAD => (),
+
+        // Deny anything else.
+        _ => {
+            return Response::builder()
+                .status(StatusCode::METHOD_NOT_ALLOWED)
+                .header(header::ALLOW, "GET, HEAD")
+                .body(Body::from("This method is not allowed\n"));
+        }
+    };
+
+    // get filename from URL with has format <scheme>://<host>/<filename>
+    let filename = req
+        .uri()
+        .path()
+        .trim_start_matches("/");
+    if filename.is_empty() {
+        return Response::builder()
+            .status(StatusCode::BAD_REQUEST)
+            .body(Body::from("Malformed request - filename expected\n"));
+    }
+
+    // construct S3 signed URL
+    let (signed_url, host) = match sign_s3(filename) {
+        Err(_) => {
+            return Response::builder()
+                .status(StatusCode::INTERNAL_SERVER_ERROR)
+                .body(Body::from("App misconfigured\n"))
+        }
+        Ok((u, h)) => (u, h),
+    };
+
+    /* Actual request to S3 */
+    let s3_req = Request::builder()
+        .method(Method::GET)
+        .uri(signed_url.as_str())
+        .header("Host", host)
+        .body(Body::empty())
+        .expect("error building the request");
+    let rsp = match fastedge::send_request(s3_req) {
+        Err(_) => {
+            return Response::builder()
+                .status(StatusCode::INTERNAL_SERVER_ERROR)
+                .body(Body::empty())
+        }
+        Ok(r) => r,
+    };
+
+    // if response is not 200, just forward it to the caller
+    let (parts, body) = rsp.into_parts();
+    if parts.status != StatusCode::OK {
+        return Ok(Response::from_parts(parts, body))
+        // if you don't want to expose S3 error to the caller, just use
+        // return Response::builder()
+        //     .status(StatusCode::INTERNAL_SERVER_ERROR)
+        //     .body(Body::empty())
+    }
+
+    // load response as image
+    let buf = body.as_bytes();
+    let out_format = match guess_format(buf) {
+        Ok(f) => f,
+        Err(_e) =>
+        // response body is not a valid image, just return it to the caller without changes
+        return Ok(Response::from_parts(parts, body))
+    };
+    let img = match load_from_memory(buf) {
+        Ok(i) => i,
+        Err(_e) =>
+            // response body is not a valid image, just return it to the caller without changes
+            return Ok(Response::from_parts(parts, body))
+    };
+
+    // load watermark as image
+    let wm_img = match load_from_memory(wm_buf.as_slice()) {
+        Ok(i) => i,
+        Err(_e) =>
+            // should never happen
+            return Response::builder()
+                .status(StatusCode::INTERNAL_SERVER_ERROR)
+                .body(Body::from("Invalid watermark format\n"))
+    };
+
+    // get opacity from env
+    let opacity = match env::var("OPACITY").ok() {
+        None => DEFAULT_OPACITY,
+        Some(l) => match l.parse::<f32>() {
+            Err(_) => return Response::builder()     // opacity is not a number
+                        .status(StatusCode::INTERNAL_SERVER_ERROR)
+                        .body(Body::from("Invalid opacity value\n")),
+            Ok(v) if v < 0.0 || v > 1.0 =>      // opacity is not in 0-1.0 range
+                    return Response::builder()
+                        .status(StatusCode::INTERNAL_SERVER_ERROR)
+                        .body(Body::from("Invalid opacity value\n")),
+            Ok(v) => v
+        },
+    }; 
+
+    let result = watermark(
+        &img,
+        &wm_img,
+        0,  // X offset for watermark placement
+        0,  // Y offset for watermark placement
+        opacity);
+
+    // convert resulting image to original format
+    let mut out = Vec::new();
+    let mut c = Cursor::new(&mut out);
+    let _ = result.write_to(&mut c, out_format);
+
+    Response::builder()
+        .status(StatusCode::OK)
+        .header(
+            header::CONTENT_TYPE,
+            out_format.to_mime_type(),
+        )
+        .body(Body::from(out))
+}
+
+// Apply watermark using alpha blending
+fn watermark(
+        img: &DynamicImage,
+        wm: &DynamicImage,
+        offset_x: u32,
+        offset_y: u32,
+        opacity: f32) -> DynamicImage {
+
+    let opacity = match opacity {
+        o if o > 1.0 => 1.0,
+        o if o < 0.0 => 0.0,
+        _ => opacity
+    };
+
+    let img_width = img.width();
+    let img_height = img.height();
+
+    let mut wm_width = wm.width();
+    let mut wm_height = wm.height();
+
+    if offset_x + wm_width > img_width {
+        wm_width = img_width - offset_x;
+    }
+
+    if offset_y + wm_height > img_height {
+        wm_height = img_height - offset_y;
+    }
+
+    let mut canvas = img.clone();
+
+    for y in 0..wm_height {
+        for x in 0..wm_width {
+            let img_x = x + offset_x;
+            let img_y = y + offset_y;
+
+            let mut img_pixel = img.get_pixel(img_x, img_y);
+            let wm_pixel = wm.get_pixel(x, y);
+
+            let img_alpha = img_pixel.0[3] as f32 / 255.0;
+            let img_red = img_pixel.0[0] as f32 * img_alpha;
+            let img_green = img_pixel.0[1] as f32 * img_alpha;
+            let img_blue = img_pixel.0[2] as f32 * img_alpha;
+
+            let wm_alpha = wm_pixel.0[3] as f32 / 255.0 * opacity;
+            let wm_red = wm_pixel.0[0] as f32 * wm_alpha;
+            let wm_green = wm_pixel.0[1] as f32 * wm_alpha;
+            let wm_blue = wm_pixel.0[2] as f32 * wm_alpha;
+
+            img_pixel.0[0] = (wm_red + (1.0 - wm_alpha) * img_red) as u8;
+            img_pixel.0[1] = (wm_green + (1.0 - wm_alpha) * img_green) as u8;
+            img_pixel.0[2] = (wm_blue + (1.0 - wm_alpha) * img_blue) as u8;
+            img_pixel.0[3] = 255;
+
+            canvas.put_pixel(img_x, img_y, img_pixel);
+        }
+    }
+
+    canvas
+}
+
+// Calculate S3 signature
+fn sign_s3(fname: &str) -> anyhow::Result<(Url, String)> {
+    /* read S3 access params from env */
+    let access_key = env::var("ACCESS_KEY")?;
+    let secret_key = env::var("SECRET_KEY")?;
+    let region = env::var("REGION")?;
+    let base_hostname = env::var("BASE_HOSTNAME")?;
+    let bucket = env::var("BUCKET")?;
+    let scheme = env::var("SCHEME").unwrap_or_else(|_| "http".to_string());
+
+    /* set S3 request params */
+    let host = region.clone() + "." + base_hostname.as_str();
+    let upload_url = scheme + "://" + host.as_str();
+    let parsed_url = upload_url.parse()?;
+    let bucket = Bucket::new(parsed_url, UrlStyle::Path, bucket, region)?;
+
+    let creds = Credentials::new(access_key, secret_key);
+    let action = bucket.get_object(Some(&creds), fname);
+    let signed_url = action.sign(Duration::from_secs(60 * 60));
+
+    Ok((signed_url, host))
+}
diff --git a/fastedge-rust-sdk/examples/watermark/src/sample.png b/fastedge-rust-sdk/examples/watermark/src/sample.png