Python Image LibraryPIL

10/13/05

PIL – What is it?

Pythonic library forLoading and Saving images (diverse

formats)Scaling, cropping, compositing, transforms,

bands (e.g. alpha channel)Drawing text and basic shapes

Akin to the program GIMP (*GIMP also has a nice python API called GIMP-Python)

PIL - Examples

Image resizing or format conversionsAdding save/load support into your application* Font support also handy

Chart generation (also see PIDDLE piddle.sf.net)Thumbnail generationWatermarking or adding legend

PIL API - Concepts

Image – from file or newly created>>> import Image

>>> im = Image.open(“vacation.jpeg")

>>> newIm = Image.new (“RGBA”, (640, 480), (255, 0, 0))

Format – file format>>> print im.mode, im.size, im.format

RGB (1024, 768) JPEG

>>> im.save (“vacation.png”) OR

>>> im.save (“vacation.png”, “PNG”)

PIL API - Concepts

Resampling Filters NEAREST, BILINEAR, BICUBIC, ANTIALIAS>>> smallIm = im.resize ( (128, 128), Image.ANTIALIAS)

Sizes – tuple of width and height

Bounding boxes – tuples of x1, y1, x2, y2 0,0 is always upper left

PIL API - Concepts

Mode – gray scale “L”, color “RGBA” “RGB”, etc. 1 (1-bit pixels, black and white, stored with one pixel per byte) L (8-bit pixels, black and white) P (8-bit pixels, mapped to any other mode using a colour palette) RGB (3x8-bit pixels, true colour) RGBA (4x8-bit pixels, true colour with transparency mask) CMYK (4x8-bit pixels, colour separation) YCbCr (3x8-bit pixels, colour video format) I (32-bit integer pixels) F (32-bit floating point pixels)

Color – specified as 32bit value, tuple, or string myColor = (255, 0, 0, 128) # full red, with 50% alpha myColor = 0x7f0000ff # full red, with 50% alpha myColor = “#00ff00” # web color myColor = “rgb (75%, 0%, 0%)” myColor = “hsl (0, 100%, 50%)”

PIL API - Concepts

Bands – the separate color channels>>> bands = im.split ()

>>> rIm = bands [0]

>>> aIm = bands [3]

>>> remadeImage = Image.merge (“RGBA”, (rIm, gIm, bIm, aIm))

>>> grayscaleIm = Image.open (“myAlpha.gif”)

>>> remadeImage = myImage.putalpha (grayscaleIm) # replace the alpha band

PIL – Slicing & Dicing

Thumbnails Modifies in-place Preserves aspect ratio

>>> myImage.thumbnail ((128, 128), Image.ANTIALIAS)

Crop>>> bounds = (100, 100, 400, 400)

>>> cutoutIm = myImage.crop (bounds)

Paste

PIL – Slicing & Dicing

Blend/composite

Rotate

Transpose ROTATE_90/180/270, FLIP_TOP_BOTTOM, FLIP_LEFT_RIGHT >>> fixedIm = myImage.transpose (ROTATE_90)

PIL - Drawing

ImageDraw module creates drawing surface for image>>> import Image, ImageDraw

>>> im = Image.open(“vacation.jpeg")

>>> drawSurface = ImageDraw.Draw (im)

>>> import Image, ImageDraw

>>> im = Image.open(“vacation.jpeg")

>>> im.getpixel ( (4,4) )

>>> im.putpixel ( (4,4), (255,0,0))

PIL - Drawing

Basic methods of drawing surface chord arc pieslice (bounds, strtAng, endAng) ellipse (bounds) line (coordSeq) point (coordSeq) polygon (coordSeq) rectangle (bounds) # first coord inclusive, second coord

exclusvie

Common optional args for these methods fill=fillColor outline=outlineColor

PIL – Drawing Text

Text>>> drawSurface = ImageDraw.Draw (im)

>>> drawable.text ((10, 10), “Hello”, fill=(255,0,0), font=None)

TrueType Font support>>>> import ImageFont

>>> ttFont = ImageFont.truetype (“arial.ttf”, 16)

>>> drawable.text ((10, 10), “Hello”, fill=(255,0,0), font=ttFont)

References

Python Image Libraryhttp://www.pythonware.com/products/pil/

Other documentation sourcesPIL Handbookhttp://effbot.org/imagingbook/Nice pdf from New Mexico Techhttp://www.nmt.edu/tcc/help/pubs/pil/

BMP

BUFR (identify only)

EPS (write-only)

FITS (identify only)

GIF

GRIB (identify only)

HDF5 (identify only)

IM

JPEG

MPEG (identify only)

MSP

PALM (write only)

PCX

PDF (write only)

PNG

PPM

TIFF

WMF (identify only)

XBM

XV Thumbnails

CUR (read only)DCX (read only) FLI, FLC (read only)FPX (read only)GBR (read only)GD (read only) ICO (read only)IMT (read only)IPTC/NAA (read only)MCIDAS (read only)MIC (read only)PCD (read only)PIXAR (read only)PSD (read only)SGI (read only)TGA (read only)WAL (read only)XPM (read only)