DrKLO/Telegram · error

%s: can only do one image transformation at a time

Error message

%s: can only do one image transformation at a time

What it means

jpegtran's select_transform() detected that a second, different image transform was requested when one is already set (transformoption.transform != JXFORM_NONE and != the new transform). Only one spatial transform (rotate/flip/transpose/crop/etc.) is allowed per invocation. It prints the message and calls usage() (which exits).

Source

Thrown at TMessagesProj/jni/mozjpeg/jpegtran.c:118

#ifdef C_MULTISCAN_FILES_SUPPORTED
  fprintf(stderr, "  -scans FILE    Create multi-scan JPEG per script FILE\n");
#endif
  exit(EXIT_FAILURE);
}


LOCAL(void)
select_transform(JXFORM_CODE transform)
/* Silly little routine to detect multiple transform options,
 * which we can't handle.
 */
{
#if TRANSFORMS_SUPPORTED
  if (transformoption.transform == JXFORM_NONE ||
      transformoption.transform == transform) {
    transformoption.transform = transform;
  } else {
    fprintf(stderr, "%s: can only do one image transformation at a time\n",
            progname);
    usage();
  }
#else
  fprintf(stderr, "%s: sorry, image transformation was not compiled\n",
          progname);
  exit(EXIT_FAILURE);
#endif
}


LOCAL(int)
parse_switches(j_compress_ptr cinfo, int argc, char **argv,
               int last_file_arg_seen, boolean for_real)
/* Parse optional switches.
 * Returns argv[] index of first file-name argument (== argc if none).
 * Any file names with indexes <= last_file_arg_seen are ignored;
 * they have presumably been processed in a previous iteration.

View on GitHub (pinned to 45ab8f4308)

Solutions

1. Run jpegtran once per transform, piping output to the next: jpegtran -rotate 90 in.jpg | jpegtran -flip horizontal > out.jpg.
2. Remove all but one transform flag from the current command.
3. For combinations that are expressible as a single transform, use that instead (e.g. transpose instead of rotate+flip).
4. Review select_transform usage to confirm only one JXFORM_* is selected.

Example fix

// before: two transforms in one call (fails)
./jpegtran -rotate 90 -flip horizontal in.jpg > out.jpg
// after: chain two invocations
./jpegtran -rotate 90 in.jpg | ./jpegtran -flip horizontal > out.jpg

/* in a CLI wrapper, count distinct transform flags before exec */
const char *tforms[] = {"-rotate","-flip","-transpose","-transverse","-trim","-crop",NULL};
int count = 0;
for (int i=1;i<argc;i++) for (int j=0;tforms[j];j++)
  if (strncmp(argv[i],tforms[j],strlen(tforms[j]))==0) count++;
if (count > 1) { fprintf(stderr,"chain transforms across invocations\n"); exit(2); }

When it happens

Trigger: Combining flags like -rotate 90 with -flip horizontal, or -transpose with -rotate, in a single jpegtran command. Each transform flag routes through select_transform, which rejects a second distinct transform.

Common situations: Attempting orthogonalize+rotate together, scripting a pipeline that accumulates flags, or misunderstanding that jpegtran requires chaining separate invocations for multiple transforms.

Related errors

• %s: must name one input and one output file
• %s: sorry, image transformation was not compiled
• %s: bogus -crop argument '%s'
• %s: skip region exceeds image height %d\n
• %s: crop dimensions exceed image dimensions %d x %d\n

AI-assisted analysis of DrKLO/Telegram@45ab8f4308 (2026-08-14). Data as JSON: /api/errors/72f7b16a32e0c011. Report an issue: GitHub.