Add metadata stripping, watermark positioning, and rename template modules

pixstrip-core/src/operations/watermark.rs

@@ -0,0 +1,31 @@
+use crate::types::Dimensions;
+use super::WatermarkPosition;
+
+pub fn calculate_position(
+    position: WatermarkPosition,
+    image_size: Dimensions,
+    watermark_size: Dimensions,
+    margin: u32,
+) -> (u32, u32) {
+    let iw = image_size.width;
+    let ih = image_size.height;
+    let ww = watermark_size.width;
+    let wh = watermark_size.height;
+
+    let center_x = (iw - ww) / 2;
+    let center_y = (ih - wh) / 2;
+    let right_x = iw - ww - margin;
+    let bottom_y = ih - wh - margin;
+
+    match position {
+        WatermarkPosition::TopLeft => (margin, margin),
+        WatermarkPosition::TopCenter => (center_x, margin),
+        WatermarkPosition::TopRight => (right_x, margin),
+        WatermarkPosition::MiddleLeft => (margin, center_y),
+        WatermarkPosition::Center => (center_x, center_y),
+        WatermarkPosition::MiddleRight => (right_x, center_y),
+        WatermarkPosition::BottomLeft => (margin, bottom_y),
+        WatermarkPosition::BottomCenter => (center_x, bottom_y),
+        WatermarkPosition::BottomRight => (right_x, bottom_y),
+    }
+}