如何在循环中保存具有不同名称的图像文件（.jpg）？ [英] How to save image files (.jpg) with different names within a loop?

问题描述

您好，



我正在尝试在C ++循环中保存具有不同名称的文件，我发现了许多解决方案，但不幸的是它没有不适合我的工作。

我的功能将QRcode保存为图像（.jpg）。执行保存的语句的语法如下：

Hello,

I'm trying to save files with different names within a loop in C++, I've found a number of solutions, but unfortunately it doesn't fit my work.
My function saves a QRcode as an image (.jpg). the syntax of the statement which does the saving is as follows:

ERRCODE _stdcall BCSaveImageA  ( t_BarCode *  pBarCode,  
  LPCSTR  lpszFileName,  
  e_IMType  eImageType,  
  LONG  lXSize,  
  LONG  lYSize,  
  DOUBLE  dXRes,  
  DOUBLE  dYRes  
 )

其中：

where:

Parameters:
[in] pBarCode Pointer to barcode structure.
[in] lpszFileName Filename
[in] eImageType Enumeration for the type of the image.
[in] lXSize X-Size of the image [pixel]. For Vector-EPS the unit is [0.001 mms]
[in] lYSize Y-Size of the image [pixel]. For Vector-EPS the unit is [0.001 mms]
[in] dXRes X-Resolution of the image [pixels / inch].
[in] dYRes Y-Resolution of the image [pixels / inch].

成功用于在程序中生成单个文件，如下所示：

which is used successfully to generate a single file in my program as follows:

eCode = BCSaveImageA(pBC,"C://webcontent/QR12.jpg", 4, LBarcodeWidth,LBarcodeHieght, dpi, dpi);

问题是如何保存具有不同名称的多个图像文件（.jpg）？我使用了for循环并尝试在上面的语句中写下新文件的名称，如下所示：

The problem is how can I save a number of image files (.jpg) with different names? I've used a for loop and tried to write the name of the new file in the above statement as follows:

eCode = BCSaveImageA(pBC,"C://webcontent/QR"+IntToStr(i)+".jpg", 4, LBarcodeWidth,LBarcodeHieght, dpi, dpi);

其中IntToStr是一个将int转换为字符串的函数

where IntToStr is a function that converts int to string

string IntToStr(int n) 
{
    stringstream result;
    result << n;
    return result.str();
}

谢谢你&最好的问候。

Rania

Thank you & Best Regards.
Rania

推荐答案

循环看起来没问题，但看不到其他代码。



一个错误是文件名需要LPCSTR这是一个C风格的字符串，所以转换你需要的C ++字符串

the loop looks OK, but can't see other code.

one mistake is the filename needs LPCSTR which is a C style string so to convert the C++ string you'd need

str.c_str()

第二个错误是串联+使用字符串而不是C字符串。

所以一个想法是适应方法：

second mistake is concatenation with + works with string but not C strings.
so one idea is to adapt method:

string IntToStr(int n) 
{
    stringstream result;
    result<< "C://webcontent/QR"<<n<<".jpg";
    return result.str();
}

然后将字符串转换为

then convert string to

LPCSTR 

您的问题是关于构建LPCSTR。



尝试以下

Your question is really about constructing a LPCSTR.

Try the following

#include<string>
using namespace std;

for(int n = 0; n < 20; n++)
{
        string filename = "C://webcontent/QR"+ to_string((_ULonglong)n) +".jpg";
        eCode = BCSaveImageA(pBC, filename.c_str(), 4, LBarcodeWidth,LBarcodeHieght, dpi, dpi);
}

如果您的编译器符合C ++ 11标准，则不需要_ULonglong强制转换。

If your compiler is C++11 compliant you wont need the _ULonglong cast.

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