Merge pull request #12989 from venalil:fix_thresholded_tiff_read

* Fix reading of black-and-white (thresholded) TIFF images

I recently updated my local OpenCV version to 3.4.3 and found out that
I could not read my TIFF images related to my project. After debugging I
found out that there has been some static analysis fixes made
that accidentally have broken reading those black-and-white TIFF images.

Commit hash in which reading of mentioned TIFF images has been broken:
cbb1e867e5

Basically the fix is to revert back to the same functionality that has been there before,
when black-and-white images are read bpp (bitspersample) is 1.
Without the case 1: this TiffDecoder::readHeader() function always return false.

* Added type and default error message

* Added stdexcept include

* Use CV_Error instead of throw std::runtime_error

* imgcodecs(test): add TIFF B/W decoding tests

modules/imgcodecs/src/grfmt_tiff.cpp

@@ -253,6 +253,10 @@ bool TiffDecoder::readHeader()
             int wanted_channels = normalizeChannelsNumber(ncn);
             switch(bpp)
             {
+                case 1:
+                    m_type = CV_MAKETYPE(CV_8U, photometric > 1 ? wanted_channels : 1);
+                    result = true;
+                    break;
                 case 8:
                     m_type = CV_MAKETYPE(CV_8U, photometric > 1 ? wanted_channels : 1);
                     result = true;
@@ -269,6 +273,8 @@ bool TiffDecoder::readHeader()
                     m_type = CV_MAKETYPE(CV_64F, photometric > 1 ? 3 : 1);
                     result = true;
                     break;
+            default:
+                CV_Error(cv::Error::StsError, "Invalid bitsperpixel value read from TIFF header! Must be 1, 8, 16, 32 or 64.");
             }
         }
     }

modules/imgcodecs/test/test_tiff.cpp

@@ -251,6 +251,32 @@ TEST(Imgcodecs_Tiff, imdecode_no_exception_temporary_file_removed)
     EXPECT_NO_THROW(cv::imdecode(buf, IMREAD_UNCHANGED));
 }
 
+
+TEST(Imgcodecs_Tiff, decode_black_and_write_image_pr12989)
+{
+    const string filename = cvtest::findDataFile("readwrite/bitsperpixel1.tiff");
+    cv::Mat img;
+    ASSERT_NO_THROW(img = cv::imread(filename, IMREAD_GRAYSCALE));
+    ASSERT_FALSE(img.empty());
+    EXPECT_EQ(64, img.cols);
+    EXPECT_EQ(64, img.rows);
+    EXPECT_EQ(CV_8UC1, img.type()) << cv::typeToString(img.type());
+    // Check for 0/255 values only: 267 + 3829 = 64*64
+    EXPECT_EQ(267, countNonZero(img == 0));
+    EXPECT_EQ(3829, countNonZero(img == 255));
+}
+
+TEST(Imgcodecs_Tiff, decode_black_and_write_image_pr12989_default)
+{
+    const string filename = cvtest::findDataFile("readwrite/bitsperpixel1.tiff");
+    cv::Mat img;
+    ASSERT_NO_THROW(img = cv::imread(filename));  // by default image type is CV_8UC3
+    ASSERT_FALSE(img.empty());
+    EXPECT_EQ(64, img.cols);
+    EXPECT_EQ(64, img.rows);
+    EXPECT_EQ(CV_8UC3, img.type()) << cv::typeToString(img.type());
+}
+
 #endif
 
 }} // namespace