gpujpeg_writer_write_exif: only generic metadata

Removed Exif custom metadata stuff altogether. On one hand this removes
functionality but Exif contains mostly useless crap and this allows to
keep it not so much complicated

As for the issue GH-100, instead of `-O enc_exif_tag=Orientation=4` (for
cmdline), one needs `-O enc_metadata=orientation=180- -O enc_hdr=Exif`
(Exif header now not implied).

Author: MartinPulec

libgpujpeg/gpujpeg_encoder.h

@@ -225,9 +225,8 @@ gpujpeg_encoder_suggest_restart_interval(const struct gpujpeg_image_parameters*
 
 /// input image is vertically flipped (bottom-up): values @ref GPUJPEG_VAL_TRUE or @ref GPUJPEG_VAL_FALSE
 #define GPUJPEG_ENC_OPT_FLIPPED_BOOL "enc_opt_flipped"
-
-/// custom exif tag in format <key>:TYPE=<value>
-#define GPUJPEG_ENC_OPT_EXIF_TAG "enc_exif_tag"
+/// set image orientation - syntax "<name>=<deg>[-]" or "help"; only if header supports (Exif, SPIFF)
+#define GPUJPEG_ENC_OPT_METADATA "enc_metadata"
 
 /**
  * remap channel order

src/gpujpeg_encoder.c

@@ -698,6 +698,41 @@ gpujpeg_opt_set_channel_remap(struct gpujpeg_coder* coder, const char* val, cons
     return GPUJPEG_NOERR;
 }
 
+static int
+add_metadata(struct gpujpeg_image_metadata* metadata, const char* config)
+{
+    if ( strstr(config, "help") != NULL ) {
+        printf(GPUJPEG_ENC_OPT_METADATA " usage:\n");
+        printf("\t" GPUJPEG_ENC_OPT_METADATA "=orientation=<deg>[-]\n");
+        printf("\t\t<deg> - clockwise rotation - 0, 90, 180 or 270 degrees\n");
+        printf("\t\t'-'   - mirror the image horizontally after rotation applied\n");
+        return GPUJPEG_ERROR;
+    }
+    if ( strstr(config, "orientation=") != config ) {
+        printf("Wrong metadata item: %s\n", config);
+        return GPUJPEG_ERROR;
+    }
+
+    const char *val = strchr(config, '=') + 1;
+    char *endptr= NULL;
+    int deg = (int) strtol(val, &endptr, 10);
+    bool flip = false;
+    if ( *endptr == '-' ) {
+        flip = true;
+        endptr += 1;
+    }
+    if ( *endptr != '\0' || deg < 0 || deg > 270 || deg % 90 != 0 ) {
+        printf("Wrong orientation value: %s\n", config);
+        return GPUJPEG_ERROR;
+    }
+
+    metadata->vals[GPUJPEG_METADATA_ORIENTATION].set = 1;
+    metadata->vals[GPUJPEG_METADATA_ORIENTATION].orient.rotation = deg / 90;
+    metadata->vals[GPUJPEG_METADATA_ORIENTATION].orient.flip = flip;
+
+    return GPUJPEG_NOERR;
+}
+
 GPUJPEG_API int
 gpujpeg_encoder_set_option(struct gpujpeg_encoder* encoder, const char *opt, const char* val)
 {
@@ -735,10 +770,8 @@ gpujpeg_encoder_set_option(struct gpujpeg_encoder* encoder, const char *opt, con
     if ( strcmp(opt, GPUJPEG_ENC_OPT_CHANNEL_REMAP) == 0 ) {
         return gpujpeg_opt_set_channel_remap(&encoder->coder, val, GPUJPEG_ENC_OPT_CHANNEL_REMAP);
     }
-    if ( strcmp(opt, GPUJPEG_ENC_OPT_EXIF_TAG) == 0 ) {
-        encoder->header_type = GPUJPEG_HEADER_EXIF;
-        return gpujpeg_exif_add_tag(&encoder->writer->exif_tags, val) ? GPUJPEG_NOERR : GPUJPEG_ERROR;
-
+    if ( strcmp(opt, GPUJPEG_ENC_OPT_METADATA) == 0 ) {
+        return add_metadata(&encoder->writer->metadata, val);
     }
     ERROR_MSG("Invalid encoder option: %s!\n", opt);
     return GPUJPEG_ERROR;
@@ -753,7 +786,7 @@ gpujpeg_encoder_print_options() {
            "] - whether is the input image should be vertically flipped (prior encode)\n");
     printf("\t" GPUJPEG_ENC_OPT_CHANNEL_REMAP "=XYZ[W] - input channel mapping, eg. '210F' for GBRX,\n"
         "\t\t'210' for GBR; special placeholders 'F' and 'Z' to set a channel to all-ones or all-zeros\n");
-    printf("\t" GPUJPEG_ENC_OPT_EXIF_TAG "=<key>=<value>|help - custom EXIF tag (use help for syntax)\n");
+    printf("\t" GPUJPEG_ENC_OPT_METADATA "=<key>=<value>|help - set image metadata\n");
 }
 
 /* Documented at declaration */