Add more filter options and improve layout

README.md

@@ -23,7 +23,8 @@ cargo run --release -- /path/to/screenshot.png
    source pixels and resets if the source dimensions change.
 3. **Freeze** holds the displayed frame and analysis; **Resume** takes the newest
    available frame. **Stop sharing** closes capture and keeps the last image.
-4. Inspect the nearest-neighbor zoomed crop. Hover for source coordinates,
+4. Inspect the nearest-neighbor zoomed crop. Zoom ranges from 0.1× to 16×,
+   starting at 1×. Hover for source coordinates,
    RGB/hex and HSV; click to copy hex. Click palette swatches to copy them too.
 5. **Save crop PNG** writes a uniquely named PNG in the system temporary directory
    and displays its path. Drop an image or click **Open image…** to browse for a file in KDE's file picker.
@@ -45,13 +46,25 @@ palette is ordered by count, then RGB for deterministic ties. Fully transparent
 pixels are excluded; partially transparent pixels retain their stored RGB values
 and count once. Pixel inspection includes HSV and relative luminance.
 
-Use **Compare vision** below the selection to show the original crop alongside
-protanopia, deuteranopia, tritanopia, or grayscale. The first three use the
+Use **Filter** below the selection to apply protanopia, deuteranopia,
+tritanopia, or grayscale directly to the crop preview, or select **Original**
+to use the live color adjustment sliders. The first three use the
 Machado–Oliveira–Fernandes full-severity model, applied in linear RGB and then
 encoded back to sRGB. Grayscale uses relative luminance and tests removal of color
 cues; it does not model all aspects of achromatopsia. Preview mode does not change
 histograms, copied pixel values, or the exported PNG: those always use the original.
 
+**Invert** replaces each RGB channel with its complement (255 minus the channel).
+With **Original** selected, adjust **Hue shift** (−180° to +180°), **Saturation**
+(−100% to +100% relative change), and **Brightness (V)** (−100 to +100 percentage
+points of HSV value). Changes update the crop preview immediately, including live
+captures. Saturation keeps neutral colors neutral; saturation and value clamp to
+their valid ranges. Brightness adjusts HSV value, not relative luminance.
+**Reset adjustments** restores the unmodified preview. Adjustments are remembered
+while another filter is selected and applied again when returning to Original.
+Filters preserve alpha and always start from source pixels, so edits do not
+accumulate rounding errors.
+
 **Vision check** automatically checks all four scenarios. It flags pairs whose
 OKLab distance falls from at least 0.08 to at most 0.04, losing at least 50% of the
 original separation. These are project-specific screening heuristics, not