feat: alpha crop limit (#27)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "spritter"
-version = "0.5.3"
+version = "0.6.0"
 edition = "2021"
 authors = ["fgardt <[email protected]>"]
 description = "Spritesheet generator for factorio"

README.md

@@ -50,6 +50,9 @@ Options:
           When set the tile resolution will be set to 64 unless specified otherwise.
       --no-crop
           Set when the sprites should not be cropped
+  -a, --crop-alpha <CROP_ALPHA>
+          Sets the max alpha value to consider a pixel as transparent [0-255].
+          Use a higher value in case your inputs have slightly transparent pixels and don't crop nicely. [default: 0]
   -s, --scale <SCALE>
           Set a scaling factor to rescale the used sprites by.
           Values < 1.0 will shrink the sprites. Values > 1.0 will enlarge them. [default: 1]

src/image_util.rs

@@ -68,7 +68,7 @@ fn load_image_from_file(path: &Path) -> ImgUtilResult<RgbaImage> {
     Ok(image)
 }
 
-pub fn crop_images(images: &mut Vec<RgbaImage>) -> ImgUtilResult<(f64, f64)> {
+pub fn crop_images(images: &mut Vec<RgbaImage>, limit: u8) -> ImgUtilResult<(f64, f64)> {
     if images.is_empty() {
         return Err(ImgUtilError::NoImagesToCrop);
     }
@@ -89,13 +89,13 @@ pub fn crop_images(images: &mut Vec<RgbaImage>) -> ImgUtilResult<(f64, f64)> {
 
         let mut x = image
             .enumerate_pixels()
-            .filter_map(|(x, _, pxl)| if pxl[3] > 0 { Some(x) } else { None })
+            .filter_map(|(x, _, pxl)| if pxl[3] > limit { Some(x) } else { None })
             .collect::<Vec<_>>();
         x.sort_unstable();
 
         let mut y = image
             .enumerate_pixels()
-            .filter_map(|(_, y, pxl)| if pxl[3] > 0 { Some(y) } else { None })
+            .filter_map(|(_, y, pxl)| if pxl[3] > limit { Some(y) } else { None })
             .collect::<Vec<_>>();
         y.sort_unstable();
 
@@ -156,8 +156,16 @@ pub fn crop_images(images: &mut Vec<RgbaImage>) -> ImgUtilResult<(f64, f64)> {
     }
 
     // calculate how the center point shifted relative to the original image
-    let shift_x = -((f64::from(raw_width - cropped_width) / 2.0) - f64::from(min_x));
-    let shift_y = -((f64::from(raw_height - cropped_height) / 2.0) - f64::from(min_y));
+    let mut shift_x = -((f64::from(raw_width - cropped_width) / 2.0) - f64::from(min_x));
+    let mut shift_y = -((f64::from(raw_height - cropped_height) / 2.0) - f64::from(min_y));
+
+    if shift_x == 0.0 {
+        shift_x = 0.0;
+    }
+
+    if shift_y == 0.0 {
+        shift_y = 0.0;
+    }
 
     trace!("shifted by ({shift_x}, {shift_y})");
 

src/main.rs

@@ -103,6 +103,11 @@ struct SpritesheetArgs {
     #[clap(long, action)]
     pub no_crop: bool,
 
+    /// Sets the max alpha value to consider a pixel as transparent [0-255].
+    /// Use a higher value in case your inputs have slightly transparent pixels and don't crop nicely.
+    #[clap(short = 'a', long, default_value_t = 0, verbatim_doc_comment)]
+    pub crop_alpha: u8,
+
     /// Set a scaling factor to rescale the used sprites by.
     /// Values < 1.0 will shrink the sprites. Values > 1.0 will enlarge them.
     #[clap(short, long, default_value_t = 1.0, verbatim_doc_comment)]
@@ -468,7 +473,7 @@ fn generate_spritesheet(
     let (shift_x, shift_y) = if args.no_crop {
         (0.0, 0.0)
     } else {
-        image_util::crop_images(&mut images)?
+        image_util::crop_images(&mut images, args.crop_alpha)?
     };
 
     #[allow(clippy::unwrap_used)]