render: --shrink N - downscale the half-block live display (1-4)

Decimates the LCD N x N before the half-block encode so the monitor pane
takes 160/N cols x 72/N rows. Display-only: capture, recording and sixel
still read the full-res framebuffer.

Decimation is max-luma pick, not box-average: terminal fonts are 1px
bright strokes on dark background, and averaging dims them into grey
mush (the 'blurry font' regression). Keeping the brightest source pixel
of each block preserves stroke brightness and hue.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/render.h b/src/render.h
index 1be1290..fed4ec8 100644
--- a/src/render.h
+++ b/src/render.h
@@ -11,6 +11,7 @@ void render_set_hud(int frameskip, bool turbo);  // update HUD readout
 // Switch terminal output to sixel graphics (scale = integer pixel zoom, >=1).
 // Pass on=false to use the default Unicode half-block renderer.
 void render_set_sixel(bool on, int scale);
+void render_set_shrink(int n);   // half-block display downscale (1-4, def 1)
 // Draw a Game Boy body/frame around the LCD (sixel output only); buttons on the
 // drawn shell light up while pressed. No effect unless sixel mode is enabled.
 void render_set_chrome(bool on);