[FIX] -out=spupng with EIA608/teletext: offset values in XML may be not correct #893

docs/CHANGES.TXT

@@ -52,6 +52,7 @@
   - Extract multiple teletext pages simultaneously with separate output files
   - Use --tpage multiple times (e.g., --tpage 100 --tpage 200)
   - Output files are named with page suffix (e.g., output_p100.srt, output_p200.srt)
+- Fix: SPUPNG subtitle offset calculation to center based on actual image dimensions
 
 - New: Added --list-tracks (-L) option to list all tracks in media files without processing
   New: Chinese, Korean, Japanese support - proper encoding and OCR.

src/lib_ccx/ccx_encoders_common.c

@@ -775,6 +775,7 @@ struct encoder_ctx *init_encoder(struct encoder_cfg *opt)
 		return NULL;
 	}
 	ctx->in_fileformat = opt->in_format;
+	ctx->is_pal = (opt->in_format == 2);
 
 	/** used in case of SUB_EOD_MARKER */
 	ctx->prev_start = -1;

src/lib_ccx/ccx_encoders_common.h

@@ -182,10 +182,10 @@ struct encoder_ctx
 
 	// OCR in SPUPNG
 	int nospupngocr;
+	int is_pal;
 
-	// Teletext multi-page output (issue #665)
-	struct ccx_s_write *tlt_out[MAX_TLT_PAGES_EXTRACT];  // Output files per teletext page
-	uint16_t tlt_out_pages[MAX_TLT_PAGES_EXTRACT];	     // Page numbers for each output slot
+	struct ccx_s_write *tlt_out[MAX_TLT_PAGES_EXTRACT]; // Output files per teletext page
+	uint16_t tlt_out_pages[MAX_TLT_PAGES_EXTRACT];       // Page numbers for each output slot
 	unsigned int tlt_srt_counter[MAX_TLT_PAGES_EXTRACT]; // SRT counter per page
 	int tlt_out_count;				     // Number of teletext output files
 };

src/lib_ccx/ccx_encoders_spupng.c

@@ -251,6 +251,9 @@ void set_spupng_offset(void *ctx, int x, int y)
 	sp->xOffset = x;
 	sp->yOffset = y;
 }
+
+// Forward declaration for calculate_spupng_offsets
+static void calculate_spupng_offsets(struct spupng_t *sp, struct encoder_ctx *ctx);
 int save_spupng(const char *filename, uint8_t *bitmap, int w, int h,
 		png_color *palette, png_byte *alpha, int nb_color)
 {
@@ -384,7 +387,7 @@ int write_cc_bitmap_as_spupng(struct cc_subtitle *sub, struct encoder_ctx *conte
 	struct cc_bitmap *rect;
 	png_color *palette = NULL;
 	png_byte *alpha = NULL;
-	int wrote_opentag = 1;
+	int wrote_opentag = 0; // Track if we actually wrote the tag
 
 	x_pos = -1;
 	y_pos = -1;
@@ -395,13 +398,11 @@ int write_cc_bitmap_as_spupng(struct cc_subtitle *sub, struct encoder_ctx *conte
 		return 0;
 
 	inc_spupng_fileindex(sp);
-	write_sputag_open(sp, sub->start_time, sub->end_time - 1);
 
 	if (sub->nb_data == 0 && (sub->flags & SUB_EOD_MARKER))
 	{
 		context->prev_start = -1;
-		if (wrote_opentag)
-			write_sputag_close(sp);
+		// No subtitle data, skip writing
 		return 0;
 	}
 	rect = sub->data;
@@ -440,7 +441,13 @@ int write_cc_bitmap_as_spupng(struct cc_subtitle *sub, struct encoder_ctx *conte
 		}
 	}
 	filename = get_spupng_filename(sp);
-	set_spupng_offset(sp, x_pos, y_pos);
+
+	// Set image dimensions for offset calculation
+	sp->img_w = width;
+	sp->img_h = height;
+
+	// Calculate centered offsets based on screen size (PAL/NTSC)
+	calculate_spupng_offsets(sp, context);
 	if (sub->flags & SUB_EOD_MARKER)
 		context->prev_start = sub->start_time;
 	pbuf = (uint8_t *)malloc(width * height);
@@ -475,6 +482,15 @@ int write_cc_bitmap_as_spupng(struct cc_subtitle *sub, struct encoder_ctx *conte
 
 	/* TODO do rectangle wise, one color table should not be used for all rectangles */
 	mapclut_paletee(palette, alpha, (uint32_t *)rect[0].data1, rect[0].nb_colors);
+
+	// Save PNG file first
+	save_spupng(filename, pbuf, width, height, palette, alpha, rect[0].nb_colors);
+	freep(&pbuf);
+
+	// Write XML tag with calculated centered offsets
+	write_sputag_open(sp, sub->start_time, sub->end_time - 1);
+	wrote_opentag = 1; // Mark that we wrote the tag
+
 #ifdef ENABLE_OCR
 	if (!context->nospupngocr)
 	{
@@ -487,8 +503,6 @@ int write_cc_bitmap_as_spupng(struct cc_subtitle *sub, struct encoder_ctx *conte
 		}
 	}
 #endif
-	save_spupng(filename, pbuf, width, height, palette, alpha, rect[0].nb_colors);
-	freep(&pbuf);
 
 end:
 	if (wrote_opentag)
@@ -991,6 +1005,8 @@ int spupng_export_string2png(struct spupng_t *sp, char *str, FILE *output)
 	*/
 
 	// Save image
+	sp->img_w = canvas_width;
+	sp->img_h = canvas_height;
 	write_image(buffer, output, canvas_width, canvas_height);
 	free(tmp);
 	free(buffer);
@@ -1081,6 +1097,28 @@ int eia608_to_str(struct encoder_ctx *context, struct eia608_screen *data, char
 
 // string needs to be in UTF-8 encoding.
 // This function will take care of encoding.
+static void calculate_spupng_offsets(struct spupng_t *sp, struct encoder_ctx *ctx)
+{
+	int screen_w = 720;
+	int screen_h;
+
+	/* Teletext is always PAL */
+	if (ctx->in_fileformat == 2 || ctx->is_pal)
+	{
+		screen_h = 576;
+	}
+	else
+	{
+		screen_h = 480;
+	}
+
+	sp->xOffset = (screen_w - sp->img_w) / 2;
+	sp->yOffset = (screen_h - sp->img_h) / 2;
+
+	// SPU / DVD requires even yOffset (interlacing)
+	if (sp->yOffset & 1)
+		sp->yOffset++;
+}
 int spupng_write_string(struct spupng_t *sp, char *string, LLONG start_time, LLONG end_time,
 			struct encoder_ctx *context)
 {
@@ -1099,6 +1137,7 @@ int spupng_write_string(struct spupng_t *sp, char *string, LLONG start_time, LLO
 	}
 	// free(string_utf32);
 	fclose(sp->fppng);
+	calculate_spupng_offsets(sp, context);
 	write_sputag_open(sp, start_time, end_time);
 	write_spucomment(sp, string);
 	write_sputag_close(sp);

src/lib_ccx/ccx_encoders_structs.h

@@ -39,6 +39,8 @@ struct spupng_t
 	int fileIndex;
 	int xOffset;
 	int yOffset;
+	int img_w;
+	int img_h;
 };
 
 #endif