🚧 Add a first version of the mozaik builder service

src/infrastructure/services/mod.rs

@@ -1 +1,2 @@
+pub(crate) mod mozaik_builder;
 pub(crate) mod random_svg_generators;

src/infrastructure/services/mozaik_builder.rs

@@ -0,0 +1,92 @@
+use std::io::Cursor;
+
+use image::imageops::FilterType;
+use image::io::Reader;
+use image::{DynamicImage, ImageFormat};
+use image::{GenericImage, RgbImage};
+use tracing::{error, warn};
+
+fn from_raw_to_image(raw: &Vec<u8>) -> Option<DynamicImage> {
+    match Reader::new(Cursor::new(raw)).with_guessed_format() {
+        Ok(reader) => match reader.decode() {
+            Ok(image) => return Some(image),
+            Err(err) => error!("Unable to decode the image: {}", err),
+        },
+        Err(err) => {
+            error!("Unable to read the image: {}", err)
+        }
+    }
+    None
+}
+
+pub fn create_mozaik(
+    width_px: u32,
+    height_px: u32,
+    images: &[Vec<u8>],
+    padding_image: &Option<Vec<u8>>,
+) -> Vec<u8> {
+    let placeholder = DynamicImage::new_rgb8(128, 128);
+
+    let images: Vec<Option<DynamicImage>> = images.iter().map(from_raw_to_image).collect();
+    let padding_image = if let Some(padding_image) = padding_image {
+        from_raw_to_image(padding_image)
+    } else {
+        None
+    };
+
+    let mut bytes: Vec<u8> = Vec::new();
+
+    let mut allocations: Vec<&Option<DynamicImage>> = vec![];
+    let mut images_per_row = 1;
+    let mut images_per_col = 1;
+
+    match images.len() {
+        0 => {
+            allocations.push(&padding_image);
+        }
+        1 => {
+            allocations.push(&images[0]);
+        }
+        2 => {
+            allocations.extend_from_slice(&[&images[0], &images[1], &images[1], &images[0]]);
+            images_per_row = 2;
+            images_per_col = 2;
+        }
+        _ => {
+            // TODO: Manage other cases
+            warn!("For now, we only manage the rendering of mozaic with less than 3 images");
+            return bytes;
+        }
+    }
+
+    let image_width_px = width_px / images_per_row;
+    let image_height_px = height_px / images_per_col;
+
+    let mut output = RgbImage::new(width_px, height_px);
+
+    let mut row_pos = 0;
+    for (index, image) in allocations.iter().enumerate() {
+        if index > 0 && index % images_per_row as usize == 0 {
+            row_pos += 1;
+        }
+
+        let col_pos = index - (images_per_row as usize * row_pos);
+
+        let image = *image;
+
+        let scaled = image
+            .as_ref()
+            .unwrap_or(&placeholder)
+            .resize_to_fill(image_width_px, image_height_px, FilterType::Nearest)
+            .into_rgb8();
+
+        let output_image_pos_x = col_pos as u32 * image_width_px;
+        let output_image_pos_y = row_pos as u32 * image_height_px;
+
+        let _ = output.copy_from(&scaled, output_image_pos_x, output_image_pos_y);
+    }
+
+    let _ = output.write_to(&mut Cursor::new(&mut bytes), ImageFormat::Jpeg);
+
+    bytes
+}