Improve OCR speed and preprocessing

VRWT_Tool/VRC_OSC/src/screen/screen_actions.py

@@ -1,6 +1,7 @@
 import pyautogui
 import pygetwindow as gw
 
+from common.env_config import getEnvFloat
 from common.project_paths import RUNTIME_DIR
 
 SCREENSHOT_PATH = RUNTIME_DIR / "latest_screenshot.png"
@@ -93,10 +94,44 @@ def getVrchatRegion():
     return left, top, width, height
 
 
-def captureVrchatWindowTo(image_path):
+def clampRatio(value):
+    return max(0.0, min(1.0, value))
+
+
+def getOcrRegion():
+    left, top, width, height = getVrchatRegion()
+
+    # Default to the lower central area. It is much faster than OCRing the
+    # whole VRChat window and usually contains chat/subtitle text.
+    crop_left = clampRatio(getEnvFloat("OCR_CROP_LEFT", 0.05))
+    crop_top = clampRatio(getEnvFloat("OCR_CROP_TOP", 0.35))
+    crop_right = clampRatio(getEnvFloat("OCR_CROP_RIGHT", 0.95))
+    crop_bottom = clampRatio(getEnvFloat("OCR_CROP_BOTTOM", 0.95))
+
+    if crop_right <= crop_left:
+        crop_left = 0.0
+        crop_right = 1.0
+
+    if crop_bottom <= crop_top:
+        crop_top = 0.0
+        crop_bottom = 1.0
+
+    region_left = left + int(width * crop_left)
+    region_top = top + int(height * crop_top)
+    region_width = max(1, int(width * (crop_right - crop_left)))
+    region_height = max(1, int(height * (crop_bottom - crop_top)))
+
+    log(
+        "INFO",
+        f"OCR crop left={region_left} top={region_top} width={region_width} height={region_height}",
+    )
+    return region_left, region_top, region_width, region_height
+
+
+def captureRegionTo(image_path, region):
     image_path.parent.mkdir(parents=True, exist_ok=True)
 
-    left, top, width, height = getVrchatRegion()
+    left, top, width, height = region
 
     image = pyautogui.screenshot(region=(left, top, width, height))
     image.save(image_path)
@@ -105,12 +140,22 @@ def captureVrchatWindowTo(image_path):
     return image_path
 
 
+def captureVrchatWindowTo(image_path):
+    return captureRegionTo(
+        image_path,
+        getVrchatRegion(),
+    )
+
+
 def captureVrchatWindow():
     return captureVrchatWindowTo(SCREENSHOT_PATH)
 
 
 def captureOcrRegion():
-    return captureVrchatWindowTo(OCR_SCREENSHOT_PATH)
+    return captureRegionTo(
+        OCR_SCREENSHOT_PATH,
+        getOcrRegion(),
+    )
 
 
 def captureScreen():