常用操作

---

合成 Image.blend(i1,i2,a)/Image.composite(i1,i2,mask)

縮略圖 thumbnail(size,filter=None)??
Modifies in-place,Preserves aspect ratio
>>> myImage.thumbnail ((128, 128), Image.ANTIALIAS)
剪切 crop(bbox)

>>> bounds = (100, 100, 400, 400)
>>> cutoutIm = myImage.crop (bounds)
粘貼 paste(i2,where,mask=None)/paste(color,box=None,mask=None)

旋轉(zhuǎn) rotate(theta)
rotated around its center

翻轉(zhuǎn)旋轉(zhuǎn) transpose(method)
ROTATE_90/180/270(clockwise), FLIP_TOP_BOTTOM(horizontal), FLIP_RIGHT_LEFT(vertical)
>>> fixedIm = myImage.transpose (ROTATE_90)

?

The Image Module

---

The Image module provides

• a class with the same name which is used to?represent a PIL image.
• The module also provides a number of?factory functions(including functions to?load images from files, and to?create new images)

圖像對(duì)象 Image?– from file or newly created

所有的圖片操作必須有一個(gè)操作對(duì)象，例如Pil提供open(filename)進(jìn)行這個(gè)過(guò)程，此后，一切關(guān)于圖片的操作均基于這個(gè)對(duì)象。有以下幾種創(chuàng)建image對(duì)象的方式：

1 Image.open(f)

>>> import Image >>> >>> Im = Image.open("lena.jpg") >>> print Im.mode,Im.size,Im.format RGB (256, 256) JPEG >>> Im.show()

如果文件不能打開(kāi)，會(huì)拋出IOError異常。

可以查看image對(duì)象的format,mode,size,palette,info幾個(gè)屬性。

調(diào)用im.show()會(huì)在圖片查看工具中顯示當(dāng)前操作的image對(duì)象。

標(biāo)準(zhǔn)版本的show方法的實(shí)現(xiàn)不太高效，因?yàn)樗劝裪mage保存到一個(gè)臨時(shí)文件，然后調(diào)用xy工具來(lái)顯示圖像。如果你沒(méi)有安裝xy，那么它就無(wú)法工作了。不過(guò)如果它可以工作，倒還是非常方便用來(lái)debug和測(cè)試。

2 Image.new(mode,size,color=None)

color的默認(rèn)值是黑色，這里我們新建一個(gè)紅色的圖像。

>>> newIm = Image.new (“RGBA”, (640, 480), (255, 0, 0)) #新建一個(gè)image對(duì)象creating images from scratch

3 Image.blend(i1,i2,a)? -- (p1 x (1 - a) + p2 x a)

選一張灰度圖(L)做背景，和雷娜圖(RGB)做blend操作

>>> Im2 = Image.open("background.jpg").convert(Im.mode) >>> Im2 = Im2.resize(Im.size) >>> Im2.show() >>> >>> img = Image.blend(Im,Im2,0.2) >>> img.show()

?

操作完畢后save(filename)用以保存這個(gè)臨時(shí)的image對(duì)象img到硬盤(pán)。

4 Image.composite(i1,i2,mask)?? --equal-sized images i1 ,i2 and mask("1", "L", or "RGBA") (p1 x (1 - m) + p2 x m)

5 Image.eval(f,i)? -- applying a function f to each pixel of image i

6 Image.merge(mode,bandList)? --Creates a multi-band image from a sequence of single-band images of equal size

以下是Image對(duì)象的全部方法：

save(f,format=None)	保存	如果f是一個(gè)file對(duì)象，必須指定format（format codes）
convert(mode)	轉(zhuǎn)換mode	?
copy()	?	?
crop(bbox)	剪切	原圖中bbox區(qū)域
filter(name)	濾鏡	the name of predefined image enhancement filters 濾鏡名字需要import ImageFilter
getbands()	通道的字符串序列	如RGB圖返回('R', 'G', 'B')
getbbox()	包含非零區(qū)域的最小bbox	?
getextrema()	最大最小像素點(diǎn)值	min&max pixel value 單通道圖：返回元組(min,max) 多通道圖：返回各個(gè)通道的元組組成的元組
getpixel(xy)	取像素點(diǎn)值	坐標(biāo)xy處的pixel value or a sequence of pixel values
histogram(mask=None)	統(tǒng)計(jì)直方圖	單通道圖：返回列表[c0, c1, ...]，ci是值為i的像素?cái)?shù) 多通道圖：a single sequence that is the concatenation of the sequences for all bands mask參數(shù):a same-sized mask image of mode "1" or "L"(include only those pixels correspond to nonzero pixels in the mask argument)
offset(dx,dy=None)	平移	Returns a new image the same size as the original, but with all pixels rotated dx in the +x direction,and dy in the +y direction. If dy is omitted, it defaults to the same value as dx.
paste(i2,where,mask=None)	粘貼圖片	where參數(shù)可以是 1 (x,y)坐標(biāo)對(duì)：i2的像素點(diǎn)(0,0)對(duì)齊原圖中的(x,y)粘貼，i2超過(guò)原圖邊界的部分被拋棄 2 bbox：i2必須和該bounding box大小一致 3 None：i2必須和原圖大小一致 如果i2的mode和原圖不一致，粘貼前會(huì)被轉(zhuǎn)換。 mask參數(shù)：a same-sized mask image of mode "1","L" or “RGBA ”(control which pixels get replaced)
paste(color,box=None,mask=None)	填充顏色	如果box省略，整個(gè)圖被填充為color色；mask參數(shù)同上
point(function)	改變像素點(diǎn)(函數(shù))	Returns a new image with each pixel modified.
point(table)	改變像素點(diǎn)(查表)	To translate pixels using a table(a sequence of 256n values, where n is the number of bands in the image) lookup
putalpha(band)	改變alpha通道	The pixels of the band image(same-sized,"L" or "1") replace the alpha band(A) of the original image(RGBA) in place.
putpixel(xy, color)	改變單個(gè)像素點(diǎn)顏色	Note that this method is relatively slow. For more extensive changes, use paste or theImageDraw?module instead.
resize(size,filter=None)	調(diào)整大小	?
rotate(theta)	旋轉(zhuǎn)（圍繞圖片中心）	? Any pixels that are not covered by rotation of the original image are set to black.
show()	顯示圖片	On Unix systems, this method runs the xv image viewer to display the image.? On Windows boxes,the image is saved in BMP format and can be viewed using Paint.? This can be useful for debugging.
split()	分離通道	返回各個(gè)通道的灰度圖組成的元組 Returns a tuple containing each band of the original image as an image of mode "L".? For example, applying this method to an "RGB" image produces a tuple of three images, one each for the red, green, and blue bands.
thumbnail(size,filter=None)	縮略圖	Modifies in-place,Preserves aspect ratio
transform(xs, ys, Image.EXTENT, (x0,y0,x1,y1))	?	Returns a transformed copy of the image. In the transformed image, the point originally at (x0,y0) will appear at (0,0), and point (x1,y1) will appear at (xs, ys).
transform(xs, ys, Image.AFFINE, (a,b,c,d,e,f))	affine變換	The values a through f are the first two rows of an affine transform matrix. Each pixel at (x,y) in the resulting image comes from position (ax+by+c,dx+ey+f) in the input image, rounded to the nearest pixel.
transpose(method)	翻轉(zhuǎn)旋轉(zhuǎn)	ROTATE_90/180/270(clockwise), FLIP_TOP_BOTTOM(horizontal), FLIP_RIGHT_LEFT(vertical)

?

The ImageDraw Module

---

支持2D圖像?The ImageDraw module provide basic 2D graphics support for Image objects.
It can for example be used to

• create new images,
• annotate or retouch existing images, and to?generate graphics on the fly for web use.

For a more advanced drawing library for PIL, see?The aggdraw Module.

創(chuàng)建繪畫(huà)對(duì)象?ImageDraw module creates drawing surface for image

import Image, ImageDraw im = Image.open(“vacation.jpeg") drawSurface = ImageDraw.Draw(im)

基本繪畫(huà)操作?Basic methods of drawing surface

• 弧/弦/扇形 chord arc pieslice (bbox, strtAng, endAng)
• 橢圓 ellipse (bbox)
• 線段/多段線 line (L)? draw.line(((60,60),(90,60), (90,90), (60,90), (60,60))) #draw a square
• 點(diǎn) point (xy)? #單像素點(diǎn)很小看不清,實(shí)際中可用實(shí)心小圓代替
• 多邊形 polygon (L) draw.polygon([(60,60), (90,60), (90,90), (60,90)]) #draw a square
• 矩形 rectangle (bbox)?????? # first coord屬于矩形, second coord不屬于
• 文字 text(xy,message,font=None) 繪制文字message，文本區(qū)域左上角坐標(biāo)為xy
  ????? drawable.text((10, 10), "Hello", fill=(255,0,0), font=None)
• 文字大小 textsize(message,font=None)? 給定文字message，返回所占像素(width,height)

可選參數(shù)?Common optional args for these methods

• fill=fillColor
• outline=outlineColor

矢量字體支持?TrueType Font support

import ImageFont ttFont = ImageFont.truetype (“arial.ttf”, 16) drawable.text ((10, 10), “Hello”, fill=(255,0,0), font=ttFont)

例子：Draw a Grey Cross Over an Image

import Image, ImageDraw im = Image.open("lena.pgm") # Creates an object that can be used to draw in the given image. draw = ImageDraw.Draw(im) # draw.line(xy, options) => Draws a line between the coordinates in the xy list.# The coordinate list can be any sequence object containing either 2-tuples [ (x, y), ... ] # or numeric values [ x, y, ... ]. # The fill option gives the color to use for the line. draw.line((0, 0) + im.size, fill=128) draw.line((0, im.size[1], im.size[0], 0), fill=128) del draw # write to stdout im.save(sys.stdout, "PNG")

?

The ImageChops module

---

a number of arithmetical image operations, called?channel operations?("chops" 通道操作).

These can be used for various purposes, including special effects 特殊效果, image compositions 圖像合成, algorithmic painting 算法繪畫(huà), and more.

At this time, channel operations are?only implemented for 8-bit images?(e.g. "L" and "RGB").

例子:比較兩幅圖像

Exact Comparison：

The quickest way to determine if two images have exactly the same contents is to get the difference between the two images, and then calculate the bounding box of the non-zero regions in this image. If the images are identical, all pixels in the difference image are zero, and the bounding box function returns?None.

import ImageChops def equal(im1, im2): return ImageChops.difference(im1, im2).getbbox() is None

To get a measure of how similar two images are, you can calculate the root-mean-square (RMS) value of the difference between the images. If the images are exactly identical, this value is zero. The following function uses the?difference?function, and then calculates the RMS value from the histogram of the resulting image.

RMS Difference：

To get a measure of how similar two images are, you can calculate the root-mean-square (RMS) value of the difference between the images. If the images are exactly identical, this value is zero. The following function uses the?difference?function, and then calculates the RMS value from the histogram of the resulting image.

# Example: File: imagediff.pyimport ImageChops import math, operator def rmsdiff(im1, im2): "Calculate the root-mean-square difference between two images" h = ImageChops.difference(im1, im2).histogram() # calculate rmsreturn math.sqrt(reduce(operator.add, map(lambda h, i: h*(i**2), h, range(256)) ) / (float(im1.size[0]) * im1.size[1]))
from:　http://www.cnblogs.com/wei-li/archive/2012/04/19/2456725.html

總結(jié)

以上是生活随笔為你收集整理的Python图像处理库：PIL中Image,ImageDraw等基本模块介绍的全部?jī)?nèi)容，希望文章能夠幫你解決所遇到的問(wèn)題。

如果覺(jué)得生活随笔網(wǎng)站內(nèi)容還不錯(cuò)，歡迎將生活随笔推薦給好友。