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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()