c++ - LibGD库不起作用:保存图像时崩溃

我一直在为C++寻找JPG保存库很长时间，但是我似乎什么都无法工作。现在我正在尝试使用LibGD:

我在做什么错？看来可行，但是保存崩溃了。码:

...
#pragma comment(lib, "bgd.lib")


#include <gd/gd.h>

...

void save_test(){
    gdImagePtr im;
    FILE *jpegout;
    int black;
    int white;
    im = gdImageCreateTrueColor(64, 64);

    black = gdImageColorAllocate(im, 0, 0, 0);
    white = gdImageColorAllocate(im, 255, 255, 255);
    gdImageLine(im, 0, 0, 63, 63, white);

    if(jpegout = fopen("test.jpg", "wb")){
        if(im){
            gdImageJpeg(im, jpegout, -1); // crash here!
        }
        fclose(jpegout);
    }

    gdImageDestroy(im);
}

我从以下位置下载了该库:http://www.libgd.org/releases/gd-latest-win32.zip

我在正确的目录等中具有库/ include / bgd.dll文件。

编辑:下面的答案包含解决了我的问题的这段代码:

int size;
char* data = (char*)gdImagePngPtr(im, &size);
fwrite(data, sizeof(char), size, out);
gdFree(data);

最佳答案

在尝试使用im和jpegout之前，请先使用它们来确保它们均已分配。

[编辑]最好从测试中拆分分配文件句柄的有效性。您尝试过the libgd example吗？

[Edit2]我下载了相同的源代码等，在VS2008中建立了一个项目，并得到了完全相同的问题。您可以尝试this suggestion ..



那里有一个代码片段，可修复我机器上的崩溃情况:

/* Bring in gd library functions */
#include "gd.h"

/* Bring in standard I/O so we can output the PNG to a file */
#include <stdio.h>

int main() {
  /* Declare the image */
  gdImagePtr im;
  /* Declare output files */
  FILE *pngout, *jpegout;
  /* Declare color indexes */
  int black;
  int white;

  /* Allocate the image: 64 pixels across by 64 pixels tall */
  im = gdImageCreate(64, 64);

  /* Allocate the color black (red, green and blue all minimum).
    Since this is the first color in a new image, it will
    be the background color. */
  black = gdImageColorAllocate(im, 0, 0, 0);

  /* Allocate the color white (red, green and blue all maximum). */
  white = gdImageColorAllocate(im, 255, 255, 255);

  /* Draw a line from the upper left to the lower right,
    using white color index. */
  gdImageLine(im, 0, 0, 63, 63, white);

  /* Open a file for writing. "wb" means "write binary", important
    under MSDOS, harmless under Unix. */
  errno_t result1 = fopen_s(&pngout, "C:\\Projects\\Experiments\\LibGD\\test.png", "wb");

  /* Do the same for a JPEG-format file. */
  errno_t result2 = fopen_s(&jpegout, "C:\\Projects\\Experiments\\LibGD\\test.jpg", "wb+");

  /* Output the image to the disk file in PNG format. */
  int size;
  char* data = (char*)gdImagePngPtr(im, &size);
  fwrite(data, sizeof(char), size, pngout);
  gdFree(data);

  data = (char*)gdImageJpegPtr(im, &size, -1);
  fwrite(data, sizeof(char), size, jpegout);
  gdFree(data);

  /* Close the files. */
  fclose(pngout);
  fclose(jpegout);

  /* Destroy the image in memory. */
  gdImageDestroy(im);
}

关于c++ - LibGD库不起作用:保存图像时崩溃，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/2307965/