text: /**
   * Basic test for gdImageContrast()
   */
  
  
  #include "gd.h"
  #include "gdtest.h"
  
  
  static void test_contrast(double contrast);
  
  
  int main()
  {
      test_contrast(+50.0);
      test_contrast(-50.0);
  
      return gdNumFailures();
  }
  
  
  static void test_contrast(double contrast)
  {
      gdImagePtr im;
      FILE *fp;
      char basename[256];
      char *path;
  
      fp = gdTestFileOpen2("gdimagecontrast", "basic.png");
      im = gdImageCreateFromPng(fp);
      fclose(fp);
  
      gdImageContrast(im, contrast);
  
      sprintf(basename, "basic%+03.0f.png", contrast);
      path = gdTestFilePath2("gdimagecontrast", basename);
      gdAssertImageEqualsToFile(path, im);
      gdFree(path);
  
      gdImageDestroy(im);
  }
  