ILPython图像处理模块.ppt

Python Image Library PIL 10/13/05 PIL What is it? Pythonic library for lLoading and Saving images (diverse formats) lScaling, cropping, compositing, transforms, bands (e.g. alpha channel) lDrawing 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 conversions Adding save/load support into your application * Font support also handy Chart generation (also see PIDDLE ) Thumbnail generation Watermarking 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 lNEAREST, BILINEAR, BICUBIC, ANTIALIAS smallIm = im.resize ( (128, 128), Image.ANTIALIAS) Sizes tuple of width and height Bounding boxes tuples of x1, y1, x2, y2 l0,0 is always upper left PIL API - Concepts Mode gray scale “L”, color “RGBA” “RGB”, etc. l1 (1-bit pixels, black and white, stored with one pixel per byte) lL (8-bit pixels, black and white) lP (8-bit pixels, mapped to any other mode using a colour palette) lRGB (3x8-bit pixels, true colour) lRGBA (4x8-bit pixels, true colour with transparency mask) lCMYK (4x8-bit pixels, colour separation) lYCbCr (3x8-bit pixels, colour video format) lI (32-bit integer pixels) lF (32-bit floating point pixels) Color specified as 32bit value, tuple, or string lmyColor = (255, 0, 0, 128) # full red, with 50% alpha lmyColor = 0x7f0000ff# full red, with 50% alpha lmyColor = “#00ff00” # web color lmyColor = “rgb (75%, 0%, 0%)” lmyColor = “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 lModifies in-place lPreserves 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 lROTATE_90/180/270, FLIP_TOP_BOTTOM, FLIP_LEFT_RIGHT l 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 lchord arc pieslice (bounds, strtAng, endAng) lellipse (bounds) lline (coordSeq) lpoint (coordSeq) lpolygon (coordSeq) lrectangle (bounds) # first coord inclusive, second coord exclusvie Common optional args for these methods lfill=fillColor loutline=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 Library l/products/pil/ Other documentation sources lPIL Handbook l/imagingbook/ lNice pdf from New Mexico Tech l/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