Python使用freetype渲染显示阿拉伯语

目录
一、使用场景
二、语言背景
三、环境搭建
四、程序结构
五、代码

一、使用场景

公司一直以点阵屏显示为业务。最近希望替换原有的点阵字库，转用FreeType渲染矢量字形，且需要支持阿拉伯语。验证可行性阶段因为python的各种库用起来相当舒服，所以就先用Python进行验证，通过后再转C++实现。

二、语言背景

阿拉伯语与常规语言不同，它属于复杂文本语言。它有以下3个特点：
1.阅读顺序从右往左
2.字符在词前中后有不同写法
3.带有修饰符号
这里非常感谢建国雄心大哥的文章。推荐大家对于阿拉伯文如果不理解可以去他的博客看看。
http://blog.sina.com.cn/s/articlelist_1569506881_0_1.html

因为阿拉伯文有以上特点，所以不能单纯的一个字符一个字符的读取并渲染，在对字符串渲染之前需要经过一次特殊处理，转成正确的Unicode码串后再使用FreeTyoe对转换后的Unicode码串进行渲染。

三、环境搭建

这里需要用到3个Python库
1.numpy
引用原因：方便对点阵数组的操作, 而且Freetype好像也用到了
安装命令：pip install numpy
2.freetype-py
引用原因：矢量字体渲染模块
安装命令：pip install freetype-py
3.matplotlib
引用原因：显示渲染结果，如果需要在别的地方显示，可以不需要
安装命令：pip install matplotlib

四、程序结构

首先，对多语言的渲染大致分为两个模块，解析模块和渲染模块。解析模块用于处理原始Unicode码；渲染模块根据Unicode码取字模并合成点阵数组。
流程大致如下：原始字符串 -> 解析模块 -> 处理后Unicode码串 -> 渲染模块 -> 点阵数组 -> 显示。
这里的解析模块本人是自己写，但是推荐使用HarfBuzz。

这里放个用matplotlib显示的效果

五、代码

解析模块

class ArabicText(object):# first, last, middle, alone   __arabic_Positions=[[ 0xfe80, 0xfe80, 0xfe80, 0xfe80],         #0x621[ 0xfe82, 0xfe81, 0xfe82, 0xfe81], [ 0xfe84, 0xfe83, 0xfe84, 0xfe83],[ 0xfe86, 0xfe85, 0xfe86, 0xfe85],[ 0xfe88, 0xfe87, 0xfe88, 0xfe87],[ 0xfe8a, 0xfe8b, 0xfe8c, 0xfe89],    [ 0xfe8e, 0xfe8d, 0xfe8e, 0xfe8d],    [ 0xfe90, 0xfe91, 0xfe92, 0xfe8f],    [ 0xfe94, 0xfe93, 0xfe94, 0xfe93],    [ 0xfe96, 0xfe97, 0xfe98, 0xfe95],    [ 0xfe9a, 0xfe9b, 0xfe9c, 0xfe99],    [ 0xfe9e, 0xfe9f, 0xfea0, 0xfe9d],    [ 0xfea2, 0xfea3, 0xfea4, 0xfea1],    [ 0xfea6, 0xfea7, 0xfea8, 0xfea5],    [ 0xfeaa, 0xfea9, 0xfeaa, 0xfea9],    [ 0xfeac, 0xfeab, 0xfeac, 0xfeab],    [ 0xfeae, 0xfead, 0xfeae, 0xfead],    [ 0xfeb0, 0xfeaf, 0xfeb0, 0xfeaf],    [ 0xfeb2, 0xfeb3, 0xfeb4, 0xfeb1],    [ 0xfeb6, 0xfeb7, 0xfeb8, 0xfeb5],    [ 0xfeba, 0xfebb, 0xfebc, 0xfeb9],    [ 0xfebe, 0xfebf, 0xfec0, 0xfebd],    [ 0xfec2, 0xfec3, 0xfec4, 0xfec1],    [ 0xfec6, 0xfec7, 0xfec8, 0xfec5],    [ 0xfeca, 0xfecb, 0xfecc, 0xfec9],    [ 0xfece, 0xfecf, 0xfed0, 0xfecd],    [ 0x63b, 0x63b, 0x63b, 0x63b],    [ 0x63c, 0x63c, 0x63c, 0x63c],    [ 0x63d, 0x63d, 0x63d, 0x63d],    [ 0x63e, 0x63e, 0x63e, 0x63e],    [ 0x63f, 0x63f, 0x63f, 0x63f],    [ 0x640, 0x640, 0x640, 0x640],    [ 0xfed2, 0xfed3, 0xfed4, 0xfed1],    [ 0xfed6, 0xfed7, 0xfed8, 0xfed5],    [ 0xfeda, 0xfedb, 0xfedc, 0xfed9],    [ 0xfede, 0xfedf, 0xfee0, 0xfedd],    [ 0xfee2, 0xfee3, 0xfee4, 0xfee1],    [ 0xfee6, 0xfee7, 0xfee8, 0xfee5],    [ 0xfeea, 0xfeeb, 0xfeec, 0xfee9],    [ 0xfeee, 0xfeed, 0xfeee, 0xfeed],    [ 0xfef0, 0xfef3, 0xfef4, 0xfeef],    [0xfef2, 0xfef3, 0xfef4, 0xfef1]]__preSet = [0x62c, 0x62d, 0x62e, 0x647, 0x639, 0x63a, 0x641, 0x642,0x62b, 0x635, 0x636, 0x637, 0x643, 0x645, 0x646, 0x62a,        0x644, 0x628, 0x64a, 0x633, 0x634, 0x638, 0x626, 0x640] __nextSet = [0x62c, 0x62d, 0x62e, 0x647, 0x639, 0x63a, 0x641, 0x642,0x62b, 0x635, 0x636, 0x637, 0x643, 0x645, 0x646, 0x62a,        0x644, 0x628, 0x64a, 0x633, 0x634, 0x638, 0x626,        0x627, 0x623, 0x625, 0x622, 0x62f, 0x630, 0x631, 0x632,        0x648, 0x624, 0x629, 0x649, 0x640]__replaceSet = [[0xFEF5,0xFEF6],[0xFEF7,0xFEF8],[0xFEF9,0xFEFA],[0xFEFB,0xFEFC]]        # 将传入的字符串转换为显示时的数组，显示时用FreeType直接取数组中的每一个值进行排版显示即可    # 返回前已经将阿拉伯文倒置(阿拉伯文从右往左书写)    @staticmethod    def Translate(text):retArr = []        textLen = len(text)lastIdx = -3    # 上一个非阿拉伯字符所在下标        begIdxs = []    # 非阿拉伯字符串开始下标集合        endIdxs = []    # 非阿拉伯字符串结束下标集合for i in range(0,textLen):            charCode = ord(text[i])            # 非阿拉伯语字符直接添加            if charCode not in range(0x621,0x6ff):                retArr.append(charCode)                arrLen = len(retArr)                # 不连续                if arrLen - 1 != lastIdx + 1:                    begIdxs.append(arrLen - 1)                # 最后一个字符是非阿拉伯字符                if i == textLen - 1:                    endIdxs.append(arrLen - 1)                lastIdx = arrLen - 1                continue            else:                arrLen = len(retArr)                # 当前阿拉伯字符的前一个字符是非阿拉伯字符                if lastIdx == arrLen-2:                    endIdxs.append(lastIdx)#----rule 1----            # 前一个字符的Unicode码            preCh = (0 if (i==0) else ord(text[i-1]))    # preCh = i==0 ? 0 : (int)text[i-1]            # 当前字符的Unicode码            ch = charCode                               # ch = (int)text[i]            # 后一个字符的Unicode码            nextCh = (0 if(i==(textLen-1)) else ord(text[i+1])) # nextCh = i == (textLen-1) ? 0 : (int)text[i+1]val = ArabicText.__GetTransform(preCh,ch,nextCh)            retArr.append(val)            #----rule 2----            replace = ArabicText.__GetContinuousWriting(preCh,ch,nextCh)            if replace > 0:                retArr.append(replace)                i = i + 2# 阿拉伯文从右往左显示，所以要把结果反过来        retArr.reverse()        ArabicText.__NonArabicReverse(retArr,begIdxs,endIdxs)        return retArr        # 处理非阿拉伯字符，非阿拉伯字符不用反转，这里把他们再反回来    @classmethod    def __NonArabicReverse(cls,charArr=[],begIdxs=[],endIdxs=[]):        lastIdx = len(charArr) - 1   # 最后一个下标        loopCnt = len(begIdxs)        for i in range(0,loopCnt):            beg = (lastIdx - endIdxs[i])            end = (lastIdx - begIdxs[i])            switchTimes = int((end + 1 - beg)/2)            for j in range(0,switchTimes):                temp = charArr[beg+j]                charArr[beg+j] = charArr[end-j]                charArr[end-j] = temp# 处理连写字符 某些情况下需要将后续两个字符替换成其他字符    @classmethod    def __GetContinuousWriting(cls,preCh=0,ch=0,nextCh=0):        retVal = 0        nextChArr = [0x622,0x623,0x625,0x627]        positionIdx = -1        charIdx = 0        if (ch == 0x644) and (nextCh in nextChArr):            charIdx = nextChArr.index(nextCh)            if preCh in cls.__preSet:                positionIdx = 1            else:                positionIdx = 0            retVal = cls.__replaceSet[charIdx][positionIdx]                return retVal# 处理字符因前连写后连写的变形    @classmethod    def __GetTransform(cls,preCh=0,ch=0,nextCh=0):        preConnect = False        nextConnect = False        positionIdx = -1        charIdx = 0# 是前连字符        if preCh in cls.__preSet:            preConnect = True            positionIdx = 0# 是后连字符        if nextCh in cls.__nextSet:            nextConnect = True            positionIdx = 1# 既是前连又是后连，等于在中间        if preConnect and nextConnect:            positionIdx = 2        # 不是前连又不是后连，等于要单独显示        elif (preConnect == False) and (nextConnect == False):            positionIdx = 3charIdx = ch - 0x621        retVal = cls.__arabic_Positions[charIdx][positionIdx]        return retVal

入口和渲染模块

# -*- coding: utf-8 -*-
import freetype
import numpy
import matplotlib.pyplot as plt
import ArabicTextHelper as Arabic
def main():text = u'شبح ، شبح الشيوعية ، يتجول في جميع أنحاء القارة الأوروبية'    textArr = []    # 处理原始字符串，生成转换后的数组     textArr = Arabic.ArabicText.Translate(text=text)# 显示转换后的数组        FreeTypeDisplay(textArr,0x33,0xe4,0xff)    def FreeTypeDisplay(textArr=[],R=255,G=255,B=255):    RGB = [('R',numpy.uint8), ('G',numpy.uint8), ('B',numpy.uint8)]    face = freetype.Face('Fonts/ARIALUNI.TTF')    face.set_char_size( 48*64 )    slot = face.glyph# First pass to compute bboxwidth, height, = 0, 0    previous = 0    # 计算总宽高    for c in textArr:        face.load_char(c)        bitmap = slot.bitmap        height = max(height, (face.size._FT_Size_Metrics.height >> 6))        kerning = face.get_kerning(previous, c)        width += (slot.advance.x >> 6) + (kerning.x >> 6)        previous = cimgBuf = numpy.zeros((height,width), dtype=numpy.ubyte)    colorBuf = numpy.zeros((height,width),dtype=RGB)# Second pass for actual renderingxBeg, yBeg = 0, 0    previous = 0    # 把每个字添加到imgBuf里    for c in textArr:        face.load_char(c)        # 可以理解为校正值        descender = (-face.size._FT_Size_Metrics.descender) >> 6        bitmap = slot.bitmap        #基线到字模顶部的距离        top = slot.bitmap_top        w = bitmap.width        h = bitmap.rows        yBeg = height - top - descender        # 间隔         kerning = face.get_kerning(previous, c)        xBeg += (kerning.x >> 6)        newChar = numpy.array(bitmap.buffer, dtype='ubyte').reshape(h,w)        yEnd = yBeg+h        xEnd = xBeg+w        # 添加到imgBuf中        imgBuf[yBeg:yEnd,xBeg:xEnd] += newChar       xBeg += (slot.advance.x >> 6)        previous = cFillColor(imgBuf,colorBuf,R,G,B)# 显示imgBuf的内容    plt.figure(figsize=(10, 10*imgBuf.shape[0]/float(imgBuf.shape[1])))    showing = colorBuf.view(dtype=numpy.uint8).reshape(colorBuf.shape[0],colorBuf.shape[1],3)    plt.imshow(showing, interpolation='nearest', origin='upper')    plt.xticks([]), plt.yticks([])    plt.show()def FillColor(srcBuf,colorBuf,R,G,B):    rows = srcBuf.shape[0]    columns = srcBuf.shape[1]    for y in range(0,rows):        for x in range(0,columns):            if srcBuf[y][x] > 0:                colorBuf[y][x] = (R,G,B)if __name__ == '__main__':    main()

参考文章
https://www.cnblogs.com/8335IT/p/8053850.html
https://blog.csdn.net/wuxinyanzi/article/details/12912533