Wire resize algorithm selection, overwrite behavior, and fix rotation/flip scope

- Add ResizeAlgorithm enum (Lanczos3/CatmullRom/Bilinear/Nearest) to core
- Thread algorithm selection from UI ComboRow through ProcessingJob to resize_image
- Add OverwriteBehavior enum (AutoRename/Overwrite/Skip) to core
- Implement overwrite handling in executor with auto-rename suffix logic
- Wire overwrite behavior from output step through to processing job
- Fix rotation/flip to apply when resize step is enabled, not just adjustments

pixstrip-core/src/executor.rs

@@ -8,7 +8,7 @@ use crate::encoder::{EncoderOptions, OutputEncoder};
 use crate::error::{PixstripError, Result};
 use crate::loader::ImageLoader;
 use crate::operations::adjustments::apply_adjustments;
-use crate::operations::resize::resize_image;
+use crate::operations::resize::resize_image_with_algorithm;
 use crate::operations::watermark::apply_watermark;
 use crate::operations::{Flip, Rotation};
 use crate::pipeline::ProcessingJob;
@@ -344,7 +344,7 @@ impl PipelineExecutor {
 
         // Resize
         if let Some(ref config) = job.resize {
-            img = resize_image(&img, config)?;
+            img = resize_image_with_algorithm(&img, config, job.resize_algorithm)?;
         }
 
         // Adjustments (brightness, contrast, saturation, effects, crop, padding)
@@ -413,6 +413,25 @@ impl PipelineExecutor {
             job.output_path_for(source, Some(output_format))
         };
 
+        // Handle overwrite behavior
+        let output_path = match job.overwrite_behavior {
+            crate::operations::OverwriteBehavior::Skip => {
+                if output_path.exists() {
+                    // Return 0 bytes written - file was skipped
+                    return Ok((input_size, 0));
+                }
+                output_path
+            }
+            crate::operations::OverwriteBehavior::AutoRename => {
+                if output_path.exists() {
+                    find_unique_path(&output_path)
+                } else {
+                    output_path
+                }
+            }
+            crate::operations::OverwriteBehavior::Overwrite => output_path,
+        };
+
         // Ensure output directory exists
         if let Some(parent) = output_path.parent() {
             std::fs::create_dir_all(parent).map_err(PixstripError::Io)?;
@@ -451,6 +470,30 @@ fn num_cpus() -> usize {
         .unwrap_or(1)
 }
 
+fn find_unique_path(path: &std::path::Path) -> std::path::PathBuf {
+    let stem = path
+        .file_stem()
+        .and_then(|s| s.to_str())
+        .unwrap_or("output");
+    let ext = path
+        .extension()
+        .and_then(|e| e.to_str())
+        .unwrap_or("bin");
+    let parent = path.parent().unwrap_or_else(|| std::path::Path::new("."));
+
+    for i in 1u32..10000 {
+        let candidate = parent.join(format!("{}_{}.{}", stem, i, ext));
+        if !candidate.exists() {
+            return candidate;
+        }
+    }
+    // Extremely unlikely fallback
+    parent.join(format!("{}_{}.{}", stem, std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .map(|d| d.as_millis())
+        .unwrap_or(0), ext))
+}
+
 fn copy_metadata_from_source(source: &std::path::Path, output: &std::path::Path) {
     // Best-effort: try to copy EXIF from source to output using little_exif.
     // If it fails (e.g. non-JPEG, no EXIF), silently continue.

pixstrip-core/src/operations/mod.rs

@@ -46,6 +46,22 @@ impl ResizeConfig {
     }
 }
 
+// --- Resize Algorithm ---
+
+#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
+pub enum ResizeAlgorithm {
+    Lanczos3,
+    CatmullRom,
+    Bilinear,
+    Nearest,
+}
+
+impl Default for ResizeAlgorithm {
+    fn default() -> Self {
+        Self::Lanczos3
+    }
+}
+
 // --- Rotation / Flip ---
 
 #[derive(Debug, Clone, Copy, Serialize, Deserialize)]
@@ -225,6 +241,21 @@ impl AdjustmentsConfig {
     }
 }
 
+// --- Overwrite Behavior ---
+
+#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
+pub enum OverwriteBehavior {
+    AutoRename,
+    Overwrite,
+    Skip,
+}
+
+impl Default for OverwriteBehavior {
+    fn default() -> Self {
+        Self::AutoRename
+    }
+}
+
 // --- Rename ---
 
 #[derive(Debug, Clone, Serialize, Deserialize)]

pixstrip-core/src/operations/resize.rs

@@ -3,11 +3,19 @@ use fast_image_resize::{images::Image, Resizer, ResizeOptions, ResizeAlg, Filter
 use crate::error::{PixstripError, Result};
 use crate::types::Dimensions;
 
-use super::ResizeConfig;
+use super::{ResizeConfig, ResizeAlgorithm};
 
 pub fn resize_image(
     src: &image::DynamicImage,
     config: &ResizeConfig,
+) -> Result<image::DynamicImage> {
+    resize_image_with_algorithm(src, config, ResizeAlgorithm::default())
+}
+
+pub fn resize_image_with_algorithm(
+    src: &image::DynamicImage,
+    config: &ResizeConfig,
+    algorithm: ResizeAlgorithm,
 ) -> Result<image::DynamicImage> {
     let original = Dimensions {
         width: src.width(),
@@ -40,7 +48,13 @@ pub fn resize_image(
     );
 
     let mut resizer = Resizer::new();
-    let options = ResizeOptions::new().resize_alg(ResizeAlg::Convolution(FilterType::Lanczos3));
+    let alg = match algorithm {
+        ResizeAlgorithm::Lanczos3 => ResizeAlg::Convolution(FilterType::Lanczos3),
+        ResizeAlgorithm::CatmullRom => ResizeAlg::Convolution(FilterType::CatmullRom),
+        ResizeAlgorithm::Bilinear => ResizeAlg::Convolution(FilterType::Bilinear),
+        ResizeAlgorithm::Nearest => ResizeAlg::Nearest,
+    };
+    let options = ResizeOptions::new().resize_alg(alg);
 
     resizer
         .resize(&src_image, &mut dst_image, &options)

pixstrip-core/src/pipeline.rs

@@ -12,6 +12,7 @@ pub struct ProcessingJob {
     #[serde(skip)]
     pub sources: Vec<ImageSource>,
     pub resize: Option<ResizeConfig>,
+    pub resize_algorithm: ResizeAlgorithm,
     pub rotation: Option<Rotation>,
     pub flip: Option<Flip>,
     pub adjustments: Option<AdjustmentsConfig>,
@@ -20,6 +21,7 @@ pub struct ProcessingJob {
     pub metadata: Option<MetadataConfig>,
     pub watermark: Option<WatermarkConfig>,
     pub rename: Option<RenameConfig>,
+    pub overwrite_behavior: OverwriteBehavior,
     pub preserve_directory_structure: bool,
     pub progressive_jpeg: bool,
     pub avif_speed: u8,
@@ -32,6 +34,7 @@ impl ProcessingJob {
             output_dir: output_dir.as_ref().to_path_buf(),
             sources: Vec::new(),
             resize: None,
+            resize_algorithm: ResizeAlgorithm::default(),
             rotation: None,
             flip: None,
             adjustments: None,
@@ -40,6 +43,7 @@ impl ProcessingJob {
             metadata: None,
             watermark: None,
             rename: None,
+            overwrite_behavior: OverwriteBehavior::default(),
             preserve_directory_structure: false,
             progressive_jpeg: false,
             avif_speed: 6,

pixstrip-core/src/preset.rs

@@ -31,6 +31,7 @@ impl Preset {
             output_dir: output_dir.into(),
             sources: Vec::new(),
             resize: self.resize.clone(),
+            resize_algorithm: crate::operations::ResizeAlgorithm::default(),
             rotation: self.rotation,
             flip: self.flip,
             adjustments: None,
@@ -39,6 +40,7 @@ impl Preset {
             metadata: self.metadata.clone(),
             watermark: self.watermark.clone(),
             rename: self.rename.clone(),
+            overwrite_behavior: crate::operations::OverwriteBehavior::default(),
             preserve_directory_structure: false,
             progressive_jpeg: false,
             avif_speed: 6,

pixstrip-gtk/src/app.rs

@@ -18,6 +18,7 @@ pub struct JobConfig {
     pub resize_width: u32,
     pub resize_height: u32,
     pub allow_upscale: bool,
+    pub resize_algorithm: u32,
     // Adjustments
     pub adjustments_enabled: bool,
     pub rotation: u32,
@@ -222,6 +223,7 @@ fn build_ui(app: &adw::Application) {
             resize_width: if remember { sess_state.resize_width.unwrap_or(1200) } else { 1200 },
             resize_height: if remember { sess_state.resize_height.unwrap_or(0) } else { 0 },
             allow_upscale: false,
+            resize_algorithm: 0,
             adjustments_enabled: false,
             rotation: 0,
             flip: 0,
@@ -1255,6 +1257,12 @@ fn run_processing(_window: &adw::ApplicationWindow, ui: &WizardUi) {
                 allow_upscale: cfg.allow_upscale,
             });
         }
+        job.resize_algorithm = match cfg.resize_algorithm {
+            1 => pixstrip_core::operations::ResizeAlgorithm::CatmullRom,
+            2 => pixstrip_core::operations::ResizeAlgorithm::Bilinear,
+            3 => pixstrip_core::operations::ResizeAlgorithm::Nearest,
+            _ => pixstrip_core::operations::ResizeAlgorithm::Lanczos3,
+        };
     }
 
     if cfg.convert_enabled {
@@ -1344,8 +1352,8 @@ fn run_processing(_window: &adw::ApplicationWindow, ui: &WizardUi) {
         });
     }
 
-    // Rotation, Flip, and Adjustments (only when adjustments step is enabled)
+    // Rotation and Flip apply from the resize step, so enable when either resize or adjustments is active
-    if cfg.adjustments_enabled {
+    if cfg.resize_enabled || cfg.adjustments_enabled {
         job.rotation = Some(match cfg.rotation {
             1 => pixstrip_core::operations::Rotation::Cw90,
             2 => pixstrip_core::operations::Rotation::Cw180,
@@ -1359,7 +1367,10 @@ fn run_processing(_window: &adw::ApplicationWindow, ui: &WizardUi) {
             2 => pixstrip_core::operations::Flip::Vertical,
             _ => pixstrip_core::operations::Flip::None,
         });
+    }
 
+    // Adjustments (brightness, contrast, etc.)
+    if cfg.adjustments_enabled {
         let crop = match cfg.crop_aspect_ratio {
             1 => Some((1.0, 1.0)),
             2 => Some((4.0, 3.0)),
@@ -1436,6 +1447,12 @@ fn run_processing(_window: &adw::ApplicationWindow, ui: &WizardUi) {
     }
 
     job.preserve_directory_structure = cfg.preserve_dir_structure;
+    job.overwrite_behavior = match cfg.overwrite_behavior {
+        1 => pixstrip_core::operations::OverwriteBehavior::AutoRename,
+        2 => pixstrip_core::operations::OverwriteBehavior::Overwrite,
+        3 => pixstrip_core::operations::OverwriteBehavior::Skip,
+        _ => pixstrip_core::operations::OverwriteBehavior::AutoRename, // 0 "Ask" defaults to auto-rename in batch
+    };
 
     drop(cfg);
 

pixstrip-gtk/src/steps/step_resize.rs

@@ -453,6 +453,12 @@ pub fn build_resize_page(state: &AppState) -> adw::NavigationPage {
             jc.borrow_mut().flip = row.selected();
         });
     }
+    {
+        let jc = state.job_config.clone();
+        algorithm_row.connect_selected_notify(move |row| {
+            jc.borrow_mut().resize_algorithm = row.selected();
+        });
+    }
 
     scrolled.set_child(Some(&content));