C和Python语言中的不同值像素！ ！ ！ [英] Different value pixel in C and Python language ! ! !
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问题描述
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
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 ++）
{
// < span class =code-comment>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);
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