【Python】Pillowで画像リサイズ・加工・編集の基本と使い方を解説

# 推奨: Pythonに紐づくpipを明示
python -m pip install --upgrade pip
python -m pip install pillow

# バージョン確認
python -c "import PIL; import PIL.Image; print(PIL.__version__)"

# 基本の開く/保存する
from PIL import Image
from pathlib import Path

img_path = Path("images/input.jpg")  # 実在のファイルに置き換えてください
out_path = Path("outputs/basic_copy.jpg")
out_path.parent.mkdir(parents=True, exist_ok=True)

# with構文で自動クローズ
with Image.open(img_path) as im:
    print("format:", im.format)  # 例: JPEG
    print("mode:", im.mode)      # 例: RGB, RGBA, L
    print("size:", im.size)      # (幅, 高さ)のタプル

    # JPEGとして保存(品質を指定)
    im.save(out_path, quality=90)
    print("saved to:", out_path)

from PIL import Image, ImageOps
from pathlib import Path

src = Path("images/input.jpg")
dst = Path("outputs/resized_800.jpg")
dst.parent.mkdir(parents=True, exist_ok=True)

with Image.open(src) as im:
    # EXIFの自動回転を反映
    im = ImageOps.exif_transpose(im)

    # 横幅を800pxに合わせて等比リサイズ
    base_w = 800
    w, h = im.size
    ratio = base_w / w
    new_size = (base_w, int(h * ratio))

    # 高品質なLANCZOSでリサイズ
    im_resized = im.resize(new_size, resample=Image.Resampling.LANCZOS)

    # JPEGとして最適化して保存
    im_resized = im_resized.convert("RGB")  # JPEGはRGB
    im_resized.save(dst, quality=90, optimize=True, progressive=True)
    print(f"resized: {w}x{h} -> {im_resized.size}, saved to {dst}")

from PIL import Image

with Image.open("images/input.jpg") as im:
    resized = im.resize((1200, 800), resample=Image.Resampling.BICUBIC)  # 幅1200, 高さ800に固定
    resized.save("outputs/resize_1200x800.jpg", quality=90)
    print("new size:", resized.size)

from PIL import Image

with Image.open("images/input.jpg") as im:
    im.thumbnail((800, 800), resample=Image.Resampling.LANCZOS)
    im.save("outputs/thumbnail_max800.jpg", quality=90)
    print("thumbnail size:", im.size)

from PIL import Image

with Image.open("images/input.jpg") as im:
    small_nearest = im.resize((400, 300), Image.Resampling.NEAREST)
    small_bicubic = im.resize((400, 300), Image.Resampling.BICUBIC)
    small_lanczos = im.resize((400, 300), Image.Resampling.LANCZOS)

    small_nearest.save("outputs/small_nearest.jpg", quality=90)
    small_bicubic.save("outputs/small_bicubic.jpg", quality=90)
    small_lanczos.save("outputs/small_lanczos.jpg", quality=90)
    print("saved 3 files with different filters")

from PIL import Image, ImageOps

def resize_by_width(src, dst, width=800):
    with Image.open(src) as im:
        im = ImageOps.exif_transpose(im)
        w, h = im.size
        if w <= width:
            out = im.copy()
        else:
            ratio = width / w
            out = im.resize((width, int(h * ratio)), Image.Resampling.LANCZOS)
        out.convert("RGB").save(dst, quality=90, optimize=True, progressive=True)
        print(f"{src} -> {dst}, {w}x{h} -> {out.size}")

resize_by_width("images/input.jpg", "outputs/width800.jpg", 800)

# ディレクトリ配下のJPEG/PNGを横幅800pxに等比リサイズして出力
from pathlib import Path
from PIL import Image, ImageOps

input_dir = Path("images")
output_dir = Path("outputs/800w")
target_w = 800

output_dir.mkdir(parents=True, exist_ok=True)
count_ok, count_ng = 0, 0

for p in input_dir.rglob("*"):
    if p.is_file() and p.suffix.lower() in (".jpg", ".jpeg", ".png"):
        try:
            with Image.open(p) as im:
                im = ImageOps.exif_transpose(im)
                w, h = im.size

                if w <= target_w:
                    out = im.copy()
                else:
                    ratio = target_w / w
                    out = im.resize((target_w, int(h * ratio)), Image.Resampling.LANCZOS)

                # JPEGで保存(透過を持つ場合は白で合成)
                out_path = output_dir / f"{p.stem}_800w.jpg"
                if out.mode in ("RGBA", "LA"):
                    bg = Image.new("RGB", out.size, (255, 255, 255))
                    bg.paste(out, mask=out.split()[-1])
                    out = bg
                else:
                    out = out.convert("RGB")

                out.save(out_path, quality=85, optimize=True, progressive=True)
                print(f"Saved: {out_path.name} ({w}x{h} -> {out.size})")
                count_ok += 1
        except Exception as e:
            print(f"Skip {p.name}: {e}")
            count_ng += 1

print(f"Done. ok={count_ok}, error={count_ng}")

from PIL import Image

with Image.open("images/input.jpg") as im:
    w, h = im.size
    # 画像中央から正方形にトリミング
    side = min(w, h)
    left = (w - side) // 2
    top = (h - side) // 2
    box = (left, top, left + side, top + side)
    cropped = im.crop(box)
    cropped.save("outputs/crop_square.jpg", quality=90)
    print("crop box:", box, "->", cropped.size)

from PIL import Image

with Image.open("images/input.jpg") as im:
    # 30度回転(キャンバス拡張、余白は白で塗る)
    rotated = im.rotate(30, expand=True, fillcolor=(255, 255, 255))
    rotated.save("outputs/rotated_30.jpg", quality=90)

    # 左右反転
    flipped = im.transpose(Image.FLIP_LEFT_RIGHT)
    flipped.save("outputs/flip_lr.jpg", quality=90)

    print("rotated:", rotated.size, "flipped:", flipped.size)

from PIL import Image, ImageEnhance

with Image.open("images/input.jpg") as im:
    # 明るさを20%上げ、コントラストを10%上げる
    brighter = ImageEnhance.Brightness(im).enhance(1.2)
    adjusted = ImageEnhance.Contrast(brighter).enhance(1.1)
    adjusted.save("outputs/bright_contrast.jpg", quality=90)
    print("enhance done")

from PIL import Image, ImageFilter

with Image.open("images/input.jpg") as im:
    blur = im.filter(ImageFilter.GaussianBlur(radius=2))
    sharp = im.filter(ImageFilter.UnsharpMask(radius=2, percent=150, threshold=3))
    edge = im.filter(ImageFilter.FIND_EDGES)

    blur.save("outputs/gaussian_blur.jpg", quality=90)
    sharp.save("outputs/unsharp.jpg", quality=90)
    edge.save("outputs/edges.jpg", quality=90)
    print("filters saved")

from PIL import Image, ImageDraw, ImageFont
from pathlib import Path

with Image.open("images/input.jpg").convert("RGBA") as base:
    draw = ImageDraw.Draw(base)

    # フォントの候補をOS毎に探す(見つからなければデフォルト)
    font_candidates = [
        "C:/Windows/Fonts/meiryo.ttc",
        "/System/Library/Fonts/Helvetica.ttc",
        "/usr/share/fonts/truetype/noto/NotoSansCJK-Regular.ttc",
    ]
    font_path = next((p for p in font_candidates if Path(p).exists()), None)
    font = ImageFont.truetype(font_path, 48) if font_path else ImageFont.load_default()

    text = "Sample Watermark"
    margin = 20

    # テキストのサイズを取得
    bbox = draw.textbbox((0, 0), text, font=font, stroke_width=2)
    tw, th = bbox[2] - bbox[0], bbox[3] - bbox[1]
    x = base.width - tw - margin
    y = base.height - th - margin

    # 半透明の背景+縁取り文字を重ねる
    overlay = Image.new("RGBA", base.size, (0, 0, 0, 0))
    o_draw = ImageDraw.Draw(overlay)
    o_draw.rectangle((x - 10, y - 5, x + tw + 10, y + th + 5), fill=(0, 0, 0, 120))
    o_draw.text((x, y), text, font=font, fill=(255, 255, 255, 230),
                stroke_width=2, stroke_fill=(0, 0, 0, 255))

    out = Image.alpha_composite(base, overlay)
    out.convert("RGB").save("outputs/text_watermark.jpg", quality=90)
    print("text placed at:", (x, y), "font:", font_path or "default")

from PIL import Image

# 背景は写真(JPEG)、ロゴは透過PNGと仮定
with Image.open("images/bg.jpg").convert("RGBA") as bg, \
     Image.open("images/logo.png").convert("RGBA") as fg:

    # 背景幅の20%にロゴを縮小
    scale = (bg.width * 0.2) / fg.width
    logo = fg.resize((int(fg.width * scale), int(fg.height * scale)), Image.Resampling.LANCZOS)

    # 左上に余白を空けて貼り付け(ロゴのアルファをマスクに使用)
    x, y = 20, 20
    bg.paste(logo, (x, y), mask=logo)

    # 最終出力をJPEGにする場合はRGBへ
    bg.convert("RGB").save("outputs/composited.jpg", quality=90)
    print("composited saved")

from PIL import Image

with Image.open("images/input.jpg") as im:
    im = ImageOps.exif_transpose(im).convert("RGB")
    im.save("outputs/q85.jpg", quality=85, optimize=True, progressive=True, subsampling=2)  # 4:2:0
    im.save("outputs/q95_high.jpg", quality=95, optimize=True, progressive=True, subsampling=0)  # 4:4:4
    print("saved q85 and q95")

from PIL import Image

with Image.open("images/icon.png").convert("RGBA") as im:
    bg = Image.new("RGB", im.size, (255, 255, 255))  # 背景は白
    bg.paste(im, mask=im.split()[-1])                # アルファをマスクに合成
    bg.save("outputs/icon_on_white.jpg", quality=90)
    print("flattened and saved to JPEG")

from pathlib import Path
from PIL import Image

src = Path(r"C:\Users\you\Pictures\サンプル.jpg")  # 生文字列で\をエスケープ不要に
dst = Path("outputs/path_test.jpg")
dst.parent.mkdir(parents=True, exist_ok=True)

with Image.open(src) as im:
    im.save(dst, quality=90)
    print("saved to:", dst.resolve())

from PIL import Image, ImageOps

with Image.open("images/phone.jpg") as im:
    print("before:", im.size, "orientation:", im.getexif().get(274))  # 274はOrientation
    fixed = ImageOps.exif_transpose(im)
    print("after :", fixed.size)

    # 可能ならEXIFを保ったまま保存
    exif_bytes = im.getexif().tobytes()
    fixed.convert("RGB").save("outputs/phone_fixed.jpg", exif=exif_bytes, quality=90)
    print("saved fixed image with EXIF")