C和Python语言中的不同值像素！ ！ ！

本文介绍了C和Python语言中的不同值像素！ ！ ！的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 嘿朋友 我试图将图像pgm（灰度）转换为图像黑白（0或255）两种颜色 我是用python语言做的，因为它的这么容易转换！在我看到python中的所有像素并且运行良好之后，我只看到了两个值255和0并且我通过GIMP打开了图像并且它全部确定 -之后我试图看到c中的所有像素语言，但显示是假的我看到打印不同于python的打印，我没有看到两种颜色只有我在像素11,200,23看到很多价值，... 我播种给你我试过我c和python语言，请问我错了！？ 我尝试了什么：

// read_image_line_by_line.cpp：定义入口点控制台应用程序。 // #include stdafx.h #include < stdio.h > #include < conio.h > void func（） { FILE * pFile; pFile = fopen（ result.pbm， rb）; char c; do { c = getc（pFile）; printf（ ％c，c）; } while （c！= EOF）; fclose（pFile）; } int _tmain（ int argc ，_TCHAR * argv []） { func（）; getch（）; }

--------------------------来自PIL import Image的--------------------------------------

image_file = Image.open（ lena512.pgm ）＃ 打开彩色图像 image_file = image_file.convert（' 1'）＃ 将图像转换为黑白 image_file.save（' 结果。 pbm'） widh，heigh = image_file.size print （widh） print （heigh） pixel_values = list（image_file.getdata（）） print （pixel_values）< /conio.h></stdio.h>

解决方案

请参阅 PBM格式 [ ^ ]。 PBM文件包含可打印的ASCII标头和像素作为打包二进制数据。使用Python代码，您将从像素数据（无标题）创建列表并打印这些值。我不知道python在内部做什么，但我想它会从打包数据中创建一个字节（或整数）列表。 在你的C代码中你正在打印ASCII标头和打包数据。要获得类似的输出，请跳过C代码中的标题并解压缩数据字节：

// 在此处读取标题并获取图像的宽度和高度 int stride = width％ 8 ; for （ int i = 0 ; i< height; i ++） { for （ int j = 0 ; j< width / 8 ; j ++） { unsigned data_byte =（ unsigned ）getc（pFile）; for （ int k = 0 ; k< 8 ; k ++） { // 这里的位顺序可能是错误的。 // 如果是这样，请检查掩码0x80并向左移动。 // 编辑：黑色是1，白色为零！ printf（ ％d，， （data_byte& 1 ）？ 0 ： 255 ）; data_byte>> = 1 ; } } if （stride） { unsigned data_byte =（ unsigned ）getc（pFile）; for （ int k = 0 ; k< stride; k ++） { // 再次：也许是订单这里的位错误。 printf（ ％d，， （data_byte& 1 ）？ 0 ： 255 ）; data_byte>> = 1 ; } } }

To解析标题最好将整个文件内容读入内存（代码未经过测试但编译）：

#include< stdio.h中> #include< io.h> #include< ctype.h> // ... FILE * pFile = fopen（result.pbm，rb）; //注意：对于Microsoft编译器，这些函数可能需要 //领先得分（_filelength，_fileno） long file_len = filelength（fileno（pFile））; unsigned char * buffer =（unsigned char *）malloc（file_len）; fread（buffer，1，file_len，pFile）; fclose（pFile）; const char * header =（const char *）buffer; //跳过幻数P4 while（isalnum（* header））header ++; //跳过空格 while（isspace（* header））header ++; //获取宽度 int width = atoi（header）; //跳过宽度 while（isdigit（* header））header ++; //跳过空格 while（isspace（* header））header ++; int height = atoi（header）; //跳过高度 while（isdigit（* header））header ++; //跳过单个空格 header ++; //指向第一个数据（像素）字节的指针 const unsigned char * data =（const unsigned char *）header; //如果宽度不是8的倍数，则每行额外字节 int stride = width％8; for（int i = 0; i< height; i ++） { for（int j = 0; j< width / 8; j ++） { unsigned data_byte = * data ++; for（int k = 0; k< 8; k ++） { //这里的比特顺序可能是错误的。 //如果是这样，请检查掩码0x80并向左移动。 //编辑：黑色为1，白色为零！ printf（％d，，（data_byte& 1）？0：255）; data_byte>> = 1; } } if（stride） { unsigned data_byte = * data ++; for（int k = 0; k< stride; k ++） { //再次：也许这里的位顺序是错误的。 printf（％d，，（data_byte& 1）？0：255）; data_byte>> = 1; } } } 免费（缓冲）;

hey friends I tried to convert image pgm (greyscale) to image black and white (0 or 255) two color I did it by python language because its so easy to convert! after I see all pixel in python and the run is good , I seen only two value 255 and 0 and I opened the image by GIMP and its all ok -after I tried to see all pixel in c language but the display is false I seen print different than the print by python , I not seen two color only I see many value in pixel 11, 200 , 23, ... I sow to you my tried I c and python language , please what my wrong !? What I have tried:

// read_image_line_by_line.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include <stdio.h> #include<conio.h> void func() { FILE *pFile; pFile = fopen("result.pbm", "rb"); char c; do { c= getc (pFile); printf("%c",c); } while (c != EOF); fclose(pFile); } int _tmain(int argc, _TCHAR* argv[]) { func(); getch(); }

---------------------------------------------------------------- from PIL import Image

image_file = Image.open("lena512.pgm") # open colour image image_file = image_file.convert('1') # convert image to black and white image_file.save('result.pbm') widh , heigh =image_file.size print (widh) print (heigh) pixel_values = list(image_file.getdata()) print (pixel_values)</conio.h></stdio.h>

解决方案

See The PBM Format[^]. The PBM file contains a printable ASCII header and the pixels as packed binary data. With your Python code you are creating a list from the pixel data (without header) and printing these values. I did not know what python is doing internally but I guess it creates a list of bytes (or integers) from the packed data. In your C code you are printing the ASCII header and the packed data as they are. To get a similar output, skip the header in your C code and unpack the data bytes:

// Read header here and get width and height of image int stride = width % 8; for (int i = 0; i < height; i++) { for (int j = 0; j < width / 8; j++) { unsigned data_byte = (unsigned)getc(pFile); for (int k = 0; k < 8; k++) { // Maybe the order of bits is wrong here. // If so check with mask 0x80 and shift left. // EDIT: Black is 1 and white is zero! printf("%d,", (data_byte & 1) ? 0 : 255); data_byte >>= 1; } } if (stride) { unsigned data_byte = (unsigned)getc(pFile); for (int k = 0; k < stride; k++) { // Again: Maybe the order of bits is wrong here. printf("%d,", (data_byte & 1) ? 0 : 255); data_byte >>= 1; } } }

[EDIT] To parse the header it would be better to read the whole file content into memory (code is not tested but compiles):

#include <stdio.h> #include <io.h> #include <ctype.h> // ... FILE *pFile = fopen("result.pbm", "rb"); // NOTE: With Microsoft compilers these functions might require a // leading under score (_filelength, _fileno) long file_len = filelength(fileno(pFile)); unsigned char *buffer = (unsigned char *)malloc(file_len); fread(buffer, 1, file_len, pFile); fclose(pFile); const char *header = (const char *)buffer; // Skip magic number "P4" while (isalnum(*header)) header++; // Skip white spaces while (isspace(*header)) header++; // Get width int width = atoi(header); // Skip width while (isdigit(*header)) header++; // Skip whitespace while (isspace(*header)) header++; int height = atoi(header); // Skip height while (isdigit(*header)) header++; // Skip single whitespace header++; // Pointer to first data (pixel) byte const unsigned char *data = (const unsigned char *)header; // Extra byte per row if width is not a multiple of 8 int stride = width % 8; for (int i = 0; i < height; i++) { for (int j = 0; j < width / 8; j++) { unsigned data_byte = *data++; for (int k = 0; k < 8; k++) { // Maybe the order of bits is wrong here. // If so check with mask 0x80 and shift left. // EDIT: Black is 1 and white is zero! printf("%d,", (data_byte & 1) ? 0 : 255); data_byte >>= 1; } } if (stride) { unsigned data_byte = *data++; for (int k = 0; k < stride; k++) { // Again: Maybe the order of bits is wrong here. printf("%d,", (data_byte & 1) ? 0 : 255); data_byte >>= 1; } } } free(buffer);