"""resize_image — Resize/crop images to target dimensions.
Supports three modes:
- contain: Fit within bounds, preserve aspect ratio (may letterbox)
- cover: Crop to fill target dimensions (no letterbox)
- stretch: Exact size, may distort aspect ratio
Uses Pillow for high-quality Lanczos resampling.
"""
import base64
import io
import logging
from PIL import Image
logger = logging.getLogger("studiomcphub.tools.resize")
MAX_INPUT_BYTES = 20 * 1024 * 1024 # 20MB input limit
MAX_DIMENSION = 8192
def resize_image(
image_b64: str,
width: int,
height: int,
mode: str = "contain",
fmt: str = "png",
quality: int = 90,
) -> dict:
"""Resize an image to target dimensions.
Args:
image_b64: Base64-encoded image (PNG/JPEG/WebP).
width: Target width (1-8192).
height: Target height (1-8192).
mode: 'contain' | 'cover' | 'stretch'.
fmt: Output format ('png', 'jpeg', 'webp').
quality: JPEG/WebP quality (1-100).
Returns:
dict with image_b64, width, height, format, original_size, mode.
"""
if not 1 <= width <= MAX_DIMENSION or not 1 <= height <= MAX_DIMENSION:
raise ValueError(f"Dimensions must be 1-{MAX_DIMENSION}. Got {width}x{height}.")
if mode not in ("contain", "cover", "stretch"):
raise ValueError(f"Invalid mode '{mode}'. Use: contain, cover, stretch.")
if fmt not in ("png", "jpeg", "webp"):
raise ValueError(f"Invalid format '{fmt}'. Use: png, jpeg, webp.")
raw = base64.b64decode(image_b64)
if len(raw) > MAX_INPUT_BYTES:
raise ValueError(f"Image too large ({len(raw)} bytes). Max {MAX_INPUT_BYTES // (1024*1024)}MB.")
img = Image.open(io.BytesIO(raw))
orig_w, orig_h = img.size
logger.info("resize_image: %dx%d -> %dx%d mode=%s", orig_w, orig_h, width, height, mode)
# Convert to RGB if saving as JPEG (no alpha)
if fmt == "jpeg" and img.mode in ("RGBA", "P", "LA"):
bg = Image.new("RGB", img.size, (255, 255, 255))
if img.mode == "P":
img = img.convert("RGBA")
bg.paste(img, mask=img.split()[-1] if "A" in img.mode else None)
img = bg
if mode == "stretch":
result = img.resize((width, height), Image.LANCZOS)
elif mode == "contain":
# Fit within bounds, preserve aspect ratio
img.thumbnail((width, height), Image.LANCZOS)
result = img
elif mode == "cover":
# Scale to cover, then center-crop
src_ratio = orig_w / orig_h
dst_ratio = width / height
if src_ratio > dst_ratio:
# Source is wider — scale by height, crop width
new_h = height
new_w = int(orig_w * (height / orig_h))
else:
# Source is taller — scale by width, crop height
new_w = width
new_h = int(orig_h * (width / orig_w))
img = img.resize((new_w, new_h), Image.LANCZOS)
left = (new_w - width) // 2
top = (new_h - height) // 2
result = img.crop((left, top, left + width, top + height))
buf = io.BytesIO()
save_kwargs = {}
if fmt == "jpeg":
save_kwargs["quality"] = quality
save_kwargs["optimize"] = True
elif fmt == "webp":
save_kwargs["quality"] = quality
elif fmt == "png":
save_kwargs["optimize"] = True
pil_fmt = {"png": "PNG", "jpeg": "JPEG", "webp": "WEBP"}[fmt]
result.save(buf, format=pil_fmt, **save_kwargs)
output_b64 = base64.b64encode(buf.getvalue()).decode("ascii")
return {
"image_b64": output_b64,
"width": result.size[0],
"height": result.size[1],
"format": fmt,
"original_size": f"{orig_w}x{orig_h}",
"output_size_bytes": len(buf.getvalue()),
"mode": mode,
}
