gardesk/garlock / 1eace39

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Optimize blur with downsample-blur-upsample

Significantly faster blur processing by:
1. Downsampling image to 1/4 resolution
2. Applying blur at reduced size (16x fewer pixels)
3. Upsampling back to original resolution

Especially beneficial on ARM where image processing is slower.
Authored by mfwolffe <wolffemf@dukes.jmu.edu>
SHA
1eace39daff3946f2b7838776263d8f3bf86148f
Parents
4c3739e
Tree
f262d2e

1 changed file

StatusFile+-
M garlock/src/background.rs 45 5
garlock/src/background.rsmodified
@@ -7,6 +7,9 @@ use image::{imageops, RgbaImage};
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 use crate::screenshot::{rgba_to_bgra, Screenshot};
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+/// Downsample factor for fast blur (blur at 1/N resolution)
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+const BLUR_DOWNSAMPLE_FACTOR: u32 = 4;
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+
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 /// Processed background ready for display
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 pub struct Background {
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     /// Pixel data in BGRA format for X11
@@ -19,6 +22,11 @@ pub struct Background {
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 impl Background {
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     /// Create a blurred background from a screenshot
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+    ///
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+    /// Uses downsample-blur-upsample for fast processing:
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+    /// 1. Shrink image to 1/4 size
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+    /// 2. Apply blur at reduced resolution (much faster)
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+    /// 3. Scale back to original size
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     pub fn from_screenshot(
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         screenshot: Screenshot,
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         blur_radius: f32,
@@ -37,9 +45,41 @@ impl Background {
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         let img = RgbaImage::from_raw(screenshot.width, screenshot.height, rgba_data)
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             .context("Failed to create image from screenshot data")?;
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-        // Apply gaussian blur
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-        tracing::debug!("Applying blur (radius={})", blur_radius);
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-        let blurred = imageops::blur(&img, blur_radius);
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+        let original_width = screenshot.width;
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+        let original_height = screenshot.height;
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+
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+        // Downsample for faster blur
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+        let small_width = original_width / BLUR_DOWNSAMPLE_FACTOR;
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+        let small_height = original_height / BLUR_DOWNSAMPLE_FACTOR;
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+
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+        tracing::debug!(
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+            original_width,
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+            original_height,
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+            small_width,
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+            small_height,
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+            "Downsampling for fast blur"
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+        );
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+
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+        let small_img = imageops::resize(
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+            &img,
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+            small_width,
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+            small_height,
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+            imageops::FilterType::Triangle,
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+        );
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+
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+        // Apply blur at reduced resolution (scale radius proportionally)
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+        let scaled_radius = blur_radius / BLUR_DOWNSAMPLE_FACTOR as f32;
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+        tracing::debug!(scaled_radius, "Applying blur at reduced resolution");
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+        let blurred_small = imageops::blur(&small_img, scaled_radius);
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+
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+        // Upsample back to original size
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+        tracing::debug!("Upsampling to original resolution");
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+        let blurred = imageops::resize(
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+            &blurred_small,
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+            original_width,
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+            original_height,
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+            imageops::FilterType::Triangle,
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+        );
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         // Apply brightness adjustment
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         tracing::debug!("Applying brightness adjustment (factor={})", brightness);
@@ -51,8 +91,8 @@ impl Background {
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         Ok(Self {
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             data: bgra_data,
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-            width: screenshot.width,
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-            height: screenshot.height,
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+            width: original_width,
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+            height: original_height,
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         })
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     }
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