app.py

import gradio as gr
from PIL import Image, ImageDraw, ImageFont
import xml.etree.ElementTree as ET
import os

# --- Helper Functions ---

def get_alto_namespace(xml_file_path):
    try:
        tree = ET.parse(xml_file_path)
        root = tree.getroot()
        if '}' in root.tag:
            return root.tag.split('}')[0] + '}'
    except ET.ParseError:
        print(f"Error parsing XML to find namespace: {xml_file_path}")
    return ''

def parse_alto_xml(xml_file_path):
    full_text_lines = []
    ocr_data = []
    if not xml_file_path or not os.path.exists(xml_file_path):
        return "Error: XML file not provided or does not exist.", []
    try:
        ns_prefix = get_alto_namespace(xml_file_path)
        tree = ET.parse(xml_file_path)
        root = tree.getroot()
        for text_line in root.findall(f'.//{ns_prefix}TextLine'):
            line_text_parts = []
            for string_element in text_line.findall(f'{ns_prefix}String'):
                text = string_element.get('CONTENT')
                if text:
                    line_text_parts.append(text)
                    try:
                        hpos = int(float(string_element.get('HPOS')))
                        vpos = int(float(string_element.get('VPOS')))
                        width = int(float(string_element.get('WIDTH')))
                        height = int(float(string_element.get('HEIGHT')))
                        ocr_data.append({
                            'text': text, 'x': hpos, 'y': vpos, 'w': width, 'h': height
                        })
                    except (ValueError, TypeError) as e:
                        print(f"Warning: Could not parse coordinates for '{text}': {e}")
                        ocr_data.append({
                            'text': text, 'x': 0, 'y': 0, 'w': 10, 'h': 10
                        })
            if line_text_parts:
                full_text_lines.append(" ".join(line_text_parts))
        return "\n".join(full_text_lines), ocr_data
    except ET.ParseError as e:
        return f"Error parsing XML: {e}", []
    except Exception as e:
        return f"An unexpected error occurred during XML parsing: {e}", []

def draw_ocr_on_image(image_pil, ocr_data):
    """
    Draws styled bounding boxes and text from ocr_data onto the image.
    """
    if not image_pil or not ocr_data:
        return image_pil

    draw = ImageDraw.Draw(image_pil)

    for item in ocr_data:
        x, y, w, h = item['x'], item['y'], item['w'], item['h']
        text = item['text']

        # 1. Draw bounding box for the original OCR segment
        draw.rectangle([(x, y), (x + w, y + h)], outline="rgba(255,0,0,190)", width=1) # Red, bit transparent

        # 2. Determine font for this specific item
        # Adaptive font size based on item height, with min/max caps
        # Making it slightly smaller relative to box height for overlay text
        current_font_size = max(8, min(16, int(item['h'] * 0.60))) 
        is_truetype = False
        try:
            font = ImageFont.truetype("arial.ttf", current_font_size)
            is_truetype = True
        except IOError:
            try:
                font = ImageFont.truetype("DejaVuSans.ttf", current_font_size)
                is_truetype = True
            except IOError:
                font = ImageFont.load_default() # Small bitmap font, size not controllable
                # print("Arial and DejaVuSans fonts not found, using default PIL font for some items.")
        
        # 3. Get actual text dimensions for precise placement
        text_actual_width = 0
        text_actual_height = 0
        text_draw_origin_is_top_left = False # Flag to know how to use coordinates with draw.text

        try: # Modern Pillow: use textbbox with anchor for precise bounds
            # Using 'lt' (left-top) anchor means (0,0) in textbbox is relative to top-left of text
            bbox = font.getbbox(text, anchor='lt') 
            text_actual_width = bbox[2] - bbox[0]
            text_actual_height = bbox[3] - bbox[1]
            text_draw_origin_is_top_left = True # draw.text with anchor='lt' will use xy as top-left
        except (AttributeError, TypeError): # Fallback for older Pillow or if anchor not supported by getbbox
            try: # Try font.getsize (deprecated but widely available)
                size = font.getsize(text)
                text_actual_width = size[0]
                if is_truetype: # For TrueType, getsize height is usually baseline to top
                    ascent, descent = font.getmetrics()
                    text_actual_height = ascent + descent # Full line height
                else: # For default font, getsize height is total height
                    text_actual_height = size[1]
            except AttributeError: # Ultimate fallback if getsize also fails (unlikely for loaded font)
                 text_actual_width = len(text) * current_font_size // 2 # Very rough estimate
                 text_actual_height = current_font_size                # Very rough estimate

        # 4. Calculate position for the TOP-LEFT of the overlay text
        buffer = 3  # Buffer in pixels between OCR box and text overlay
        text_draw_x = x # Align left edge of text with left edge of box
        
        # Try to place text above the box
        tentative_text_top_y = y - text_actual_height - buffer
        if tentative_text_top_y < buffer: # If it goes off (or too close to) the top of the image
            tentative_text_top_y = y + h + buffer # Place it below the box
        
        # Ensure it doesn't go off the bottom either
        if tentative_text_top_y + text_actual_height > image_pil.height - buffer:
            tentative_text_top_y = image_pil.height - text_actual_height - buffer # Pin to bottom
            if tentative_text_top_y < buffer: # If image is too short for text, pin to top
                tentative_text_top_y = buffer 

        final_text_top_y = tentative_text_top_y
        
        # 5. Draw background for the overlay text
        bg_padding = 2
        bg_x0 = text_draw_x - bg_padding
        bg_y0 = final_text_top_y - bg_padding
        bg_x1 = text_draw_x + text_actual_width + bg_padding
        bg_y1 = final_text_top_y + text_actual_height + bg_padding
        
        draw.rectangle([(bg_x0, bg_y0), (bg_x1, bg_y1)], fill="rgba(255, 255, 220, 235)") # Light yellow, fairly opaque

        # 6. Draw the overlay text
        draw_coords = (text_draw_x, final_text_top_y)
        if text_draw_origin_is_top_left:
            try:
                draw.text(draw_coords, text, fill="black", font=font, anchor='lt')
            except (TypeError, AttributeError): # Fallback if anchor='lt' fails at draw time
                # This fallback means background might be slightly off if is_truetype and text_draw_origin_is_top_left was True due to getbbox working
                # but draw.text doesn't support anchor. For simplicity, draw at top_y assuming it's baseline.
                 ascent = font.getmetrics()[0] if is_truetype else text_actual_height
                 draw.text((text_draw_x, final_text_top_y + ascent if is_truetype else final_text_top_y), text, fill="black", font=font)
        else: # Older Pillow, (x,y) is baseline for TrueType, top-left for default
            if is_truetype:
                ascent, _ = font.getmetrics()
                draw.text((text_draw_x, final_text_top_y + ascent), text, fill="black", font=font)
            else: # Default font, (x,y) is top-left
                draw.text((text_draw_x, final_text_top_y), text, fill="black", font=font)
            
    return image_pil

# --- Gradio Interface Function ---

def process_image_and_xml(image_path, xml_path, show_overlay):
    if image_path is None:
        return None, "Please upload an image.", None
    try:
        img_pil = Image.open(image_path).convert("RGB")
    except Exception as e:
        return None, f"Error loading image: {e}", None

    if xml_path is None:
        return img_pil, "Please upload an OCR XML file.", None

    extracted_text, ocr_box_data = parse_alto_xml(xml_path)
    overlay_image_pil = None
    if show_overlay:
        if ocr_box_data:
            img_for_overlay = img_pil.copy()
            overlay_image_pil = draw_ocr_on_image(img_for_overlay, ocr_box_data)
        elif not (isinstance(extracted_text, str) and extracted_text.startswith("Error")):
            if isinstance(extracted_text, str):
                extracted_text += "\n(No bounding box data for overlay)"
            else:
                extracted_text = "(No bounding box data for overlay)"
    return img_pil, extracted_text, overlay_image_pil

# --- Create Gradio App ---
with gr.Blocks(theme=gr.themes.Soft()) as demo:
    gr.Markdown("# OCR Viewer (ALTO XML)")
    gr.Markdown(
        "Upload an image and its corresponding ALTO OCR XML file. "
        "The app will display the image, extract and show the plain text, "
        "and optionally overlay the OCR predictions on the image."
    )
    with gr.Row():
        with gr.Column(scale=1):
            image_input = gr.File(label="Upload Image (PNG, JPG, etc.)", type="filepath")
            xml_input = gr.File(label="Upload ALTO XML File (.xml)", type="filepath")
            show_overlay_checkbox = gr.Checkbox(label="Show OCR Overlay on Image", value=False)
            submit_button = gr.Button("Process Files", variant="primary")
    with gr.Row():
        with gr.Column(scale=1):
            output_image_orig = gr.Image(label="Uploaded Image", type="pil", interactive=False)
        with gr.Column(scale=1):
            output_text = gr.Textbox(label="Extracted Plain Text", lines=15, interactive=False)
    output_image_overlay = gr.Image(label="Image with OCR Overlay", type="pil", interactive=False, visible=True)

    def update_interface(image_filepath, xml_filepath, show_overlay_val):
        if image_filepath is None and xml_filepath is None:
            return None, "Please upload an image and an XML file.", None
        img, text, overlay_img = process_image_and_xml(image_filepath, xml_filepath, show_overlay_val)
        return img, text, overlay_img

    submit_button.click(
        fn=update_interface,
        inputs=[image_input, xml_input, show_overlay_checkbox],
        outputs=[output_image_orig, output_text, output_image_overlay]
    )
    show_overlay_checkbox.change(
        fn=update_interface,
        inputs=[image_input, xml_input, show_overlay_checkbox],
        outputs=[output_image_orig, output_text, output_image_overlay]
    )
    gr.Markdown("---")
    gr.Markdown("### Example ALTO XML Snippet (for `String` element extraction):")
    gr.Code(
        value="""
<alto xmlns="http://www.loc.gov/standards/alto/v3/alto.xsd">
  <Description>...</Description>
  <Styles>...</Styles>
  <Layout>
    <Page ID="Page13" PHYSICAL_IMG_NR="13" WIDTH="2394" HEIGHT="3612">
      <PrintSpace>
        <TextLine WIDTH="684" HEIGHT="108" ID="p13_t1" HPOS="465" VPOS="196">
          <String ID="p13_w1" CONTENT="Introduction" HPOS="465" VPOS="196" WIDTH="684" HEIGHT="108" STYLEREFS="font0"/>
        </TextLine>
        <!-- ... more TextLine and String elements ... -->
      </PrintSpace>
    </Page>
  </Layout>
</alto>
        """,
        interactive=False
    )

if __name__ == "__main__":
    try:
        img_test = Image.new('RGB', (2394, 3612), color = 'lightgray')
        img_test.save("dummy_image.png")
        print("Created dummy_image.png for testing.")
        example_xml_filename = "189819724.34.xml"
        if not os.path.exists(example_xml_filename):
            print(f"WARNING: Example XML '{example_xml_filename}' not found. Please create it (using the content from the prompt) or upload your own.")
    except ImportError:
        print("Pillow not installed, can't create dummy image.")
    except Exception as e:
        print(f"Error during setup: {e}")
    demo.launch()