TurboJPEG: Use 4:4:4 for lossless JPEG buf calcs

java/TJUnitTest.java

@@ -814,6 +814,9 @@ final class TJUnitTest {
     int size, quality = 100;
     byte[] dstBuf;
 
+    if (lossless && subsamp != TJ.SAMP_GRAY)
+      subsamp = TJ.SAMP_444;
+
     dstBuf = new byte[TJ.bufSize(w, h, subsamp)];
 
     try {

tjunittest.c

@@ -537,6 +537,9 @@ static void doTest(int w, int h, const int *formats, int nformats, int subsamp,
   unsigned long size = 0;
   int pfi, pf, i, quality = 100;
 
+  if (lossless && subsamp != TJSAMP_GRAY)
+    subsamp = TJSAMP_444;
+
   if (!alloc)
     size = tjBufSize(w, h, subsamp);
   if (size != 0)

turbojpeg-jni.c

@@ -231,6 +231,8 @@ static jint TJCompressor_compress
   arraySize = (y + height - 1) * actualPitch + (x + width) * tjPixelSize[pf];
   if ((*env)->GetArrayLength(env, src) * srcElementSize < arraySize)
     THROW_ARG("Source buffer is not large enough");
+  if (flags & TJFLAG_LOSSLESS && jpegSubsamp != TJSAMP_GRAY)
+    jpegSubsamp = TJSAMP_444;
   jpegSize = tjBufSize(width, height, jpegSubsamp);
   if ((*env)->GetArrayLength(env, dst) < (jsize)jpegSize)
     THROW_ARG("Destination buffer is not large enough");

turbojpeg.c

@@ -746,6 +746,8 @@ DLLEXPORT int tjCompress2(tjhandle handle, const unsigned char *srcBuf,
   else if (flags & TJFLAG_FORCESSE) PUTENV_S("JSIMD_FORCESSE", "1");
   else if (flags & TJFLAG_FORCESSE2) PUTENV_S("JSIMD_FORCESSE2", "1");
 #endif
+  if (flags & TJFLAG_LOSSLESS && jpegSubsamp != TJSAMP_GRAY)
+    jpegSubsamp = TJSAMP_444;
 
   if (flags & TJFLAG_NOREALLOC) {
     alloc = FALSE;  *jpegSize = tjBufSize(width, height, jpegSubsamp);