Add flag for Page Segmentation Modes control (#1601)

* Add flag for Page Segmentation Modes control

I added an flag --psm for controlling PSM (Page Segmentation Modes) in Tesseract. The default option (3) gives me quite bad results. When I use 6, 11, or 12 for Bulgarian, it gives me much better OCR results. I haven't tested other languages yet, but I expect improvements as well if other mode is used.

* feat: add psm for rust parser

* fix: add psm to options

* fix: add default value of psm to 3

* fix: correct type of ocr oem

* fix(rust): use fatal! instead of exit

---------

Co-authored-by: Prateek Sunal <prtksunal@gmail.com>

docs/CHANGES.TXT

@@ -35,6 +35,7 @@
 - Fix: infinite loop in MP4 file type detector.
 - Improvement: Use Corrosion to build Rust code
 - Improvement: Ignore MXF Caption Essence Container version byte to enhance SRT subtitle extraction compatibility
+- New: Add tesseract page segmentation modes control with `--psm` flag
 
 0.94 (2021-12-14)
 -----------------

src/lib_ccx/ccx_common_option.c

@@ -72,6 +72,7 @@ void init_options(struct ccx_s_options *options)
 	options->dvblang = NULL;	  // By default, autodetect DVB language
 	options->ocrlang = NULL;	  // By default, autodetect .traineddata file
 	options->ocr_oem = -1;		  // By default, OEM mode depends on the tesseract version
+	options->psm = 3;		  // Default PSM mode (3 is the default tesseract as well)
 	options->ocr_quantmode = 1;	  // CCExtractor's internal
 	options->mkvlang = NULL;	  // By default, all the languages are extracted
 	options->ignore_pts_jumps = 1;

src/lib_ccx/ccx_common_option.h

@@ -147,6 +147,7 @@ struct ccx_s_options // Options from user parameters
 	char *dvblang;                    // The name of the language stream for DVB
 	const char *ocrlang;              // The name of the .traineddata file to be loaded with tesseract
 	int ocr_oem;                      // The Tesseract OEM mode, could be 0 (default), 1 or 2
+	int psm;						  // The Tesseract PSM mode, could be between 0 and 13. 3 is tesseract default
 	int ocr_quantmode;				  // How to quantize the bitmap before passing to to tesseract (0=no quantization at all, 1=CCExtractor's internal)
 	char *mkvlang;                    // The name of the language stream for MKV
 	int analyze_video_stream;         // If 1, the video stream will be processed even if we're using a different one for subtitles.

src/lib_ccx/ocr.c

@@ -177,6 +177,9 @@ void *init_ocr(int lang_index)
 				       &pars_values, 1, false);
 	}
 
+	// set PSM mode
+	TessBaseAPISetPageSegMode(ctx->api, ccx_options.psm);
+
 	free(pars_vec);
 	free(pars_values);
 

src/lib_ccx/params.c

@@ -679,6 +679,23 @@ void print_usage(void)
 	mprint("                       Default value depends on the tesseract version linked :\n");
 	mprint("                       Tesseract v3 : default mode is 0,\n");
 	mprint("                       Tesseract v4 : default mode is 1.\n");
+	mprint("                 --psm: Select the PSM mode for Tesseract.\n");
+	mprint("                       Available Page segmentation modes:\n");
+	mprint("                       0    Orientation and script detection (OSD) only.\n");
+	mprint("                       1    Automatic page segmentation with OSD.\n");
+	mprint("                       2    Automatic page segmentation, but no OSD, or OCR.\n");
+	mprint("                       3    Fully automatic page segmentation, but no OSD. (Default)\n");
+	mprint("                       4    Assume a single column of text of variable sizes.\n");
+	mprint("                       5    Assume a single uniform block of vertically aligned text.\n");
+	mprint("                       6    Assume a single uniform block of text.\n");
+	mprint("                       7    Treat the image as a single text line.\n");
+	mprint("                       8    Treat the image as a single word.\n");
+	mprint("                       9    Treat the image as a single word in a circle.\n");
+	mprint("                       10    Treat the image as a single character.\n");
+	mprint("                       11    Sparse text. Find as much text as possible in no particular order.\n");
+	mprint("                       12    Sparse text with OSD.\n");
+	mprint("                       13    Raw line. Treat the image as a single text line,\n");
+	mprint("                       bypassing hacks that are Tesseract-specific.\n");
 	mprint("             --mkvlang: For MKV subtitles, select which language's caption\n");
 	mprint("                       stream will be processed. e.g. 'eng' for English.\n");
 	mprint("                       Language codes can be either the 3 letters bibliographic\n");
@@ -1696,6 +1713,27 @@ int parse_parameters(struct ccx_s_options *opt, int argc, char *argv[])
 				fatal(EXIT_MALFORMED_PARAMETER, "--oem has no argument.\n");
 			}
 		}
+		if (strcmp(argv[i], "--psm") == 0)
+		{
+			if (i < argc - 1)
+			{
+				i++;
+
+				char *str = (char *)malloc(sizeof(argv[i]));
+				sprintf(str, "%s", argv[i]);
+				opt->psm = atoi(str);
+				if (opt->psm < 0 || opt->psm > 13)
+				{
+					fatal(EXIT_MALFORMED_PARAMETER, "--psm must be between 0 and 13\n");
+				}
+
+				continue;
+			}
+			else
+			{
+				fatal(EXIT_MALFORMED_PARAMETER, "--psm has no argument.\n");
+			}
+		}
 		if (strcmp(argv[i], "--mkvlang") == 0)
 		{
 			if (i < argc - 1)

src/lib_ccx/params_dump.c

@@ -216,6 +216,8 @@ void params_dump(struct lib_ccx_ctx *ctx)
 			mprint("Reduced color palette]\n");
 			break;
 	}
+
+	mprint("[Tesseract PSM: %d]\n", ccx_options.psm);
 }
 
 #define Y_N(cond) ((cond) ? "Yes" : "No")

src/rust/lib_ccxr/src/common/options.rs

@@ -455,6 +455,8 @@ pub struct Options {
     pub ocrlang: PathBuf,
     /// The Tesseract OEM mode, could be 0 (default), 1 or 2
     pub ocr_oem: i8,
+    /// The Tesseract PSM mode, could be between 0 and 13. 3 is tesseract default
+    pub psm: i32,
     /// How to quantize the bitmap before passing to to tesseract
     /// (0 = no quantization at all, 1 = CCExtractor's internal,
     ///  2 = reduce distinct color count in image for faster results.)
@@ -589,6 +591,7 @@ impl Default for Options {
             dvblang: Default::default(),
             ocrlang: Default::default(),
             ocr_oem: -1,
+            psm: 3,
             ocr_quantmode: 1,
             mkvlang: Default::default(),
             analyze_video_stream: Default::default(),

src/rust/src/args.rs

@@ -600,6 +600,25 @@ pub struct Args {
     /// Tesseract v4 : default mode is 1.
     #[arg(long, verbatim_doc_comment, value_name="mode", help_heading=OUTPUT_AFFECTING_OUTPUT_FILES)]
     pub oem: Option<u8>,
+    /// Select the PSM mode for Tesseract.
+    /// Available Page segmentation modes:
+    /// 0    Orientation and script detection (OSD) only.
+    /// 1    Automatic page segmentation with OSD.
+    /// 2    Automatic page segmentation, but no OSD, or OCR.
+    /// 3    Fully automatic page segmentation, but no OSD. (Default)
+    /// 4    Assume a single column of text of variable sizes.
+    /// 5    Assume a single uniform block of vertically aligned text.
+    /// 6    Assume a single uniform block of text.
+    /// 7    Treat the image as a single text line.
+    /// 8    Treat the image as a single word.
+    /// 9    Treat the image as a single word in a circle.
+    /// 10    Treat the image as a single character.
+    /// 11    Sparse text. Find as much text as possible in no particular order.
+    /// 12    Sparse text with OSD.
+    /// 13    Raw line. Treat the image as a single text line,
+    /// bypassing hacks that are Tesseract-specific.
+    #[arg(long, verbatim_doc_comment, value_name="mode", help_heading=OUTPUT_AFFECTING_OUTPUT_FILES)]
+    pub psm: Option<u8>,
     /// For MKV subtitles, select which language's caption
     /// stream will be processed. e.g. 'eng' for English.
     /// Language codes can be either the 3 letters bibliographic

src/rust/src/parser.rs

@@ -801,6 +801,16 @@ impl OptionsExt for Options {
             self.ocr_oem = *oem as _;
         }
 
+        if let Some(ref psm) = args.psm {
+            if !(0..=13).contains(psm) {
+                fatal!(
+                    cause = ExitCause::MalformedParameter;
+                   "--psm must be between 0 and 13"
+                );
+            }
+            self.psm = *psm as _;
+        }
+
         if let Some(ref lang) = args.mkvlang {
             self.mkvlang = Some(Language::from_str(lang.as_str()).unwrap());
             let str = lang.as_str();