test image hint: complete command-line

If used from gpujpegtool, it was not clear that also dummy output
filename should be also presented (because it is checked whether the
count of images is even - both in and out).

+ example with noise pattern

Author: MartinPulec

src/gpujpeg_common.c

@@ -416,7 +416,7 @@ gpujpeg_image_get_file_format(const char* filename)
             return extensions[i].format;
         }
     }
-    printf("\nUse \"help.tst\" for test image usage.\n");
+    printf("\nUse \"help.tst\" (eg. `gpujpegtool help.tst null.jpg`) for test image usage).\n");
     return GPUJPEG_IMAGE_FILE_UNKNOWN;
 }
 

src/utils/image_delegate.c

@@ -262,6 +262,7 @@ tst_usage()
            "\t- 1920x1080.tst              - use FullHD image\n"
            "\t- 1920x1080.c_ycbcr-jpeg.tst - \" with YCbCr color space\n"
            "\t- 1920x1080.p_u8.tst         - FHD grayscale (u8 pixel format)\n"
+           "\t- 1920x1080.noise.tst        - FHD RGB noise\n"
            "\t- 1920x1080.c_ycbcr-jpeg.p_422-u8-p1020.tst - YCbCr 4:2:2\n");
     printf("\n");
 }