Merge pull request #1989 from uploadcare/jpeg-loading-without-convertion

Use RGBX rawmode for RGB JPEG images

decode.c

@@ -819,6 +819,7 @@ PyImaging_JpegDecoderNew(PyObject* self, PyObject* args)
     char* jpegmode; /* what's in the file */
     int scale = 1;
     int draft = 0;
+
     if (!PyArg_ParseTuple(args, "ssz|ii", &mode, &rawmode, &jpegmode,
                           &scale, &draft))
         return NULL;
@@ -830,6 +831,13 @@ PyImaging_JpegDecoderNew(PyObject* self, PyObject* args)
     if (decoder == NULL)
         return NULL;
 
+    // libjpeg-turbo supports different output formats.
+    // We are choosing Pillow's native format (3 color bytes + 1 padding)
+    // to avoid extra conversion in Unpack.c.
+    if (ImagingJpegUseJCSExtensions() && strcmp(rawmode, "RGB") == 0) {
+        rawmode = "RGBX";
+    }
+
     if (get_unpacker(decoder, mode, rawmode) < 0)
         return NULL;
 

encode.c

@@ -691,6 +691,13 @@ PyImaging_JpegEncoderNew(PyObject* self, PyObject* args)
     if (encoder == NULL)
         return NULL;
 
+    // libjpeg-turbo supports different output formats.
+    // We are choosing Pillow's native format (3 color bytes + 1 padding)
+    // to avoid extra conversion in Pack.c.
+    if (ImagingJpegUseJCSExtensions() && strcmp(rawmode, "RGB") == 0) {
+        rawmode = "RGBX";
+    }
+
     if (get_packer(encoder, mode, rawmode) < 0)
         return NULL;
 
@@ -719,6 +726,8 @@ PyImaging_JpegEncoderNew(PyObject* self, PyObject* args)
 
     encoder->encode = ImagingJpegEncode;
 
+    strncpy(((JPEGENCODERSTATE*)encoder->state.context)->rawmode, rawmode, 8);
+
     ((JPEGENCODERSTATE*)encoder->state.context)->quality = quality;
     ((JPEGENCODERSTATE*)encoder->state.context)->qtables = qarrays;
     ((JPEGENCODERSTATE*)encoder->state.context)->qtablesLen = qtablesLen;

libImaging/Imaging.h

@@ -407,6 +407,7 @@ extern int ImagingHexDecode(Imaging im, ImagingCodecState state,
 extern int ImagingJpegDecode(Imaging im, ImagingCodecState state,
 			     UINT8* buffer, int bytes);
 extern int ImagingJpegDecodeCleanup(ImagingCodecState state);
+extern int ImagingJpegUseJCSExtensions(void);
 
 extern int ImagingJpegEncode(Imaging im, ImagingCodecState state,
 			     UINT8* buffer, int bytes);

libImaging/Jpeg.h

@@ -88,6 +88,9 @@ typedef struct {
     /* Chroma Subsampling (-1=default, 0=none, 1=medium, 2=high) */
     int subsampling;
 
+    /* Converter input mode (input to the shuffler) */
+    char rawmode[8+1];
+
     /* Custom quantization tables () */
     unsigned int *qtables;
 

libImaging/JpegDecode.c

@@ -38,6 +38,35 @@
 #include "Jpeg.h"
 
 
+#define STRINGIFY(x) #x
+#define TOSTRING(x) STRINGIFY(x)
+
+// There is no way to compare versions on compile time,
+// so we have to do that in runtime.
+#ifdef LIBJPEG_TURBO_VERSION
+char *libjpeg_turbo_version = TOSTRING(LIBJPEG_TURBO_VERSION);
+#else
+char *libjpeg_turbo_version = NULL;
+#endif
+
+int
+ImagingJpegUseJCSExtensions()
+{
+    int use_jcs_extensions = 0;
+    #ifdef JCS_EXTENSIONS
+        #if defined(LIBJPEG_TURBO_VERSION_NUMBER)
+            #if LIBJPEG_TURBO_VERSION_NUMBER >= 1002010
+                use_jcs_extensions = 1;
+            #endif
+        #else
+            if (libjpeg_turbo_version) {
+                use_jcs_extensions = strcmp(libjpeg_turbo_version, "1.2.1") >= 0;
+            }
+        #endif
+    #endif
+    return use_jcs_extensions;
+}
+
 /* -------------------------------------------------------------------- */
 /* Suspending input handler                                             */
 /* -------------------------------------------------------------------- */
@@ -189,6 +218,10 @@ ImagingJpegDecode(Imaging im, ImagingCodecState state, UINT8* buf, int bytes)
             context->cinfo.out_color_space = JCS_GRAYSCALE;
         else if (strcmp(context->rawmode, "RGB") == 0)
             context->cinfo.out_color_space = JCS_RGB;
+    #ifdef JCS_EXTENSIONS
+        else if (strcmp(context->rawmode, "RGBX") == 0)
+                context->cinfo.out_color_space = JCS_EXT_RGBX;
+    #endif
         else if (strcmp(context->rawmode, "CMYK") == 0 ||
                  strcmp(context->rawmode, "CMYK;I") == 0)
             context->cinfo.out_color_space = JCS_CMYK;

libImaging/JpegEncode.c

@@ -135,6 +135,10 @@ ImagingJpegEncode(Imaging im, ImagingCodecState state, UINT8* buf, int bytes)
         case 32:
             context->cinfo.input_components = 4;
             context->cinfo.in_color_space = JCS_CMYK;
+        #ifdef JCS_EXTENSIONS
+            if (strcmp(context->rawmode, "RGBX") == 0)
+                context->cinfo.in_color_space = JCS_EXT_RGBX;
+        #endif
             break;
         default:
             state->errcode = IMAGING_CODEC_CONFIG;