add live brightness/exposure controls and a webcam.conf config file

exec-cycle.sh's live preview now shows brightness/exposure and lets
+/-, ./, adjust them per-frame via fswebcam --set, with r to reset;
webcam.conf centralizes the starting values, step size, capture
resolution/quality, and the v4l2 control names (which vary by camera)
so hardware-specific tuning doesn't require editing the scripts.

exec-cycle.sh

@@ -2,22 +2,50 @@
 
 trap 'stty sane; clear; exit 0' SIGINT SIGTERM
 
+dir="$(dirname "$0")"
+[ -f "$dir/webcam.conf" ] && source "$dir/webcam.conf"
+
+BRIGHTNESS="${DEFAULT_BRIGHTNESS:-auto}"
+EXPOSURE="${DEFAULT_EXPOSURE:-auto}"
+STEP="${STEP:-5}"
+
+# clamps $1+$2 to 0-100, treating "auto" as a 50 starting point
+adjust() {
+    local cur=$1 delta=$2 val
+    [ "$cur" = "auto" ] && cur=50
+    val=$((cur + delta))
+    (( val < 0 )) && val=0
+    (( val > 100 )) && val=100
+    echo "$val"
+}
+
 while true; do
     clear
+    export BRIGHTNESS EXPOSURE
     ./webcam2ascii.sh
     echo
-    echo "[c] capture   [Ctrl+C] quit"
+    echo "brightness: ${BRIGHTNESS}   exposure: ${EXPOSURE}"
+    echo "[+/-] brightness   [./,] exposure   [r] reset to auto   [c] capture   [Ctrl+C] quit"
 
-    if read -n 1 -t 0.05 -s key && [[ "$key" == "c" || "$key" == "C" ]]; then
-        timestamp=$(date +%Y%m%d-%H%M%S)
-        cp web-cam-shot.jpg "photo-$timestamp.jpg"
-        cp ascii-img.txt "ascii-img-$timestamp.txt"
-        clear
-        cat "ascii-img-$timestamp.txt"
-        echo
-        echo "Saved photo-$timestamp.jpg and ascii-img-$timestamp.txt"
-        ./txt2printr.sh "ascii-img-$timestamp.txt"
-        read -n 1 -s -p "Press any key to resume live preview, Ctrl+C to quit..."
+    if read -n 1 -t 0.05 -s key; then
+        case "$key" in
+            "+") BRIGHTNESS=$(adjust "$BRIGHTNESS" "$STEP") ;;
+            "-") BRIGHTNESS=$(adjust "$BRIGHTNESS" "-$STEP") ;;
+            ".") EXPOSURE=$(adjust "$EXPOSURE" "$STEP") ;;
+            ",") EXPOSURE=$(adjust "$EXPOSURE" "-$STEP") ;;
+            r|R) BRIGHTNESS="${DEFAULT_BRIGHTNESS:-auto}"; EXPOSURE="${DEFAULT_EXPOSURE:-auto}" ;;
+            c|C)
+                timestamp=$(date +%Y%m%d-%H%M%S)
+                cp web-cam-shot.jpg "photo-$timestamp.jpg"
+                cp ascii-img.txt "ascii-img-$timestamp.txt"
+                clear
+                cat "ascii-img-$timestamp.txt"
+                echo
+                echo "Saved photo-$timestamp.jpg and ascii-img-$timestamp.txt"
+                ./txt2printr.sh "ascii-img-$timestamp.txt"
+                read -n 1 -s -p "Press any key to resume live preview, Ctrl+C to quit..."
+                ;;
+        esac
     fi
 done
 

webcam.conf

@@ -0,0 +1,19 @@
+# ASCII Photobooth webcam configuration
+# Sourced by webcam2ascii.sh and exec-cycle.sh.
+
+# Capture settings
+RESOLUTION=640x480
+JPEG_QUALITY=85
+
+# Starting brightness/exposure (0-100, or "auto" for the camera default)
+# exec-cycle.sh's live +/- and ./, controls adjust away from these at runtime
+DEFAULT_BRIGHTNESS=auto
+DEFAULT_EXPOSURE=auto
+
+# Step size (percentage points) for each live-preview +/- adjustment
+STEP=5
+
+# v4l2 control names as reported by: fswebcam --list-controls
+# These vary per camera/driver - edit to match your hardware
+BRIGHTNESS_CONTROL="Brightness"
+EXPOSURE_CONTROL="Exposure (Absolute)"

webcam2ascii.sh

@@ -1,5 +1,23 @@
 #/bin/bash
+#
+# Captures a frame and converts it to ascii art.
+# Reads defaults from webcam.conf. BRIGHTNESS/EXPOSURE env vars (set by
+# exec-cycle.sh's live preview controls) override the config's defaults.
 
-fswebcam -q --no-banner -r 640x480 --jpeg 85 web-cam-shot.jpg &> /dev/null
+dir="$(dirname "$0")"
+[ -f "$dir/webcam.conf" ] && source "$dir/webcam.conf"
+
+: "${RESOLUTION:=640x480}"
+: "${JPEG_QUALITY:=85}"
+: "${BRIGHTNESS:=${DEFAULT_BRIGHTNESS:-auto}}"
+: "${EXPOSURE:=${DEFAULT_EXPOSURE:-auto}}"
+: "${BRIGHTNESS_CONTROL:=Brightness}"
+: "${EXPOSURE_CONTROL:=Exposure (Absolute)}"
+
+set_opts=()
+[ "$BRIGHTNESS" != "auto" ] && set_opts+=(--set "${BRIGHTNESS_CONTROL}=${BRIGHTNESS}%")
+[ "$EXPOSURE" != "auto" ] && set_opts+=(--set "${EXPOSURE_CONTROL}=${EXPOSURE}%")
+
+fswebcam -q --no-banner -r "$RESOLUTION" --jpeg "$JPEG_QUALITY" "${set_opts[@]}" web-cam-shot.jpg &> /dev/null
 ascii-image-converter web-cam-shot.jpg | tee ascii-img.txt