diff --git a/src/canonmn_int.cpp b/src/canonmn_int.cpp
index 8432a1f32b..28e77fb759 100644
--- a/src/canonmn_int.cpp
+++ b/src/canonmn_int.cpp
@@ -11,6 +11,7 @@
 #include "error.hpp"
 #include "exif.hpp"
 #include "i18n.h"  // NLS support.
+#include "image_int.hpp"
 #include "makernote_int.hpp"
 #include "tags_int.hpp"
 #include "types.hpp"
@@ -2833,16 +2834,11 @@ std::ostream& CanonMakerNote::print0x0008(std::ostream& os, const Value& value,
 }
 
 std::ostream& CanonMakerNote::print0x000a(std::ostream& os, const Value& value, const ExifData*) {
-  std::istringstream is(value.toString());
-  uint32_t l = 0;
-  is >> l;
-  return os << std::setw(4) << std::setfill('0') << std::hex << ((l & 0xffff0000) >> 16) << std::setw(5)
-            << std::setfill('0') << std::dec << (l & 0x0000ffff);
+  uint32_t l = std::stoul(value.toString());
+  return os << stringFormat("{:04x}{:05}", (l >> 16) & 0xFFFF, l & 0xFFFF);
 }
 
 std::ostream& CanonMakerNote::print0x000c(std::ostream& os, const Value& value, const ExifData* exifData) {
-  std::istringstream is(value.toString());
-
   if (!exifData) {
     return os << value;
   }
@@ -2851,10 +2847,8 @@ std::ostream& CanonMakerNote::print0x000c(std::ostream& os, const Value& value,
   auto pos = exifData->findKey(key);
   // if model is EOS D30
   if (pos != exifData->end() && pos->value().count() == 1 && pos->value().toInt64() == 0x01140000) {
-    uint32_t l = 0;
-    is >> l;
-    return os << std::setw(4) << std::setfill('0') << std::hex << ((l & 0xffff0000) >> 16) << std::setw(5)
-              << std::setfill('0') << std::dec << (l & 0x0000ffff);
+    uint32_t l = std::stoul(value.toString());
+    return os << stringFormat("{:04x}{:05}", (l >> 16) & 0xFFFF, l & 0xFFFF);
   }
   return os << value;
 }
diff --git a/src/convert.cpp b/src/convert.cpp
index 55ed8e8194..5aad179d72 100644
--- a/src/convert.cpp
+++ b/src/convert.cpp
@@ -742,11 +742,13 @@ void Converter::cnvExifVersion(const char* from, const char* to) {
     return;
   if (!prepareXmpTarget(to))
     return;
-  std::ostringstream value;
-  for (size_t i = 0; i < pos->count(); ++i) {
-    value << static_cast<char>(pos->toInt64(i));
+  auto count = pos->count();
+  std::string value;
+  value.reserve(count);
+  for (size_t i = 0; i < count; ++i) {
+    value += static_cast<char>(pos->toInt64(i));
   }
-  (*xmpData_)[to] = value.str();
+  (*xmpData_)[to] = value;
   if (erase_)
     exifData_->erase(pos);
 }
@@ -757,13 +759,13 @@ void Converter::cnvExifGPSVersion(const char* from, const char* to) {
     return;
   if (!prepareXmpTarget(to))
     return;
-  std::ostringstream value;
+  std::string value;
   for (size_t i = 0; i < pos->count(); ++i) {
     if (i > 0)
-      value << '.';
-    value << pos->toInt64(i);
+      value += '.';
+    value += std::to_string(pos->toInt64(i));
   }
-  (*xmpData_)[to] = value.str();
+  (*xmpData_)[to] = value;
   if (erase_)
     exifData_->erase(pos);
 }
@@ -826,9 +828,7 @@ void Converter::cnvExifGPSCoord(const char* from, const char* to) {
   double min = (deg[0] * 60.0) + deg[1] + (deg[2] / 60.0);
   auto ideg = static_cast<int>(min / 60.0);
   min -= ideg * 60;
-  std::ostringstream oss;
-  oss << ideg << "," << std::fixed << std::setprecision(7) << min << refPos->toString().c_str()[0];
-  (*xmpData_)[to] = oss.str();
+  (*xmpData_)[to] = stringFormat("{},{:.7f}{}", ideg, min, refPos->toString().front());
 
   if (erase_)
     exifData_->erase(pos);
@@ -883,7 +883,7 @@ void Converter::cnvXmpArray(const char* from, const char* to) {
   auto pos = xmpData_->findKey(XmpKey(from));
   if (pos == xmpData_->end())
     return;
-  std::ostringstream array;
+  std::string array;
   for (size_t i = 0; i < pos->count(); ++i) {
     std::string value = pos->toString(i);
     if (!pos->value().ok()) {
@@ -892,11 +892,11 @@ void Converter::cnvXmpArray(const char* from, const char* to) {
 #endif
       return;
     }
-    array << value;
+    array += value;
     if (i != pos->count() - 1)
-      array << " ";
+      array += " ";
   }
-  (*exifData_)[to] = array.str();
+  (*exifData_)[to] = array;
   if (erase_)
     xmpData_->erase(pos);
 }
@@ -997,12 +997,9 @@ void Converter::cnvXmpVersion(const char* from, const char* to) {
 #endif
     return;
   }
-  std::ostringstream array;
 
-  array << static_cast<int>(value[0]) << " " << static_cast<int>(value[1]) << " " << static_cast<int>(value[2]) << " "
-        << static_cast<int>(value[3]);
-
-  (*exifData_)[to] = array.str();
+  (*exifData_)[to] = stringFormat("{} {} {} {}", static_cast<int>(value[0]), static_cast<int>(value[1]),
+                                  static_cast<int>(value[2]), static_cast<int>(value[3]));
   if (erase_)
     xmpData_->erase(pos);
 }
@@ -1234,7 +1231,7 @@ void Converter::cnvXmpValueToIptc(const char* from, const char* to) {
 
 #ifdef EXV_HAVE_XMP_TOOLKIT
 std::string Converter::computeExifDigest(bool tiff) {
-  std::ostringstream res;
+  std::string res;
   MD5_CTX context;
   unsigned char digest[16];
 
@@ -1247,9 +1244,9 @@ std::string Converter::computeExifDigest(bool tiff) {
       if (!tiff && key.groupName() == "Image")
         continue;
 
-      if (!res.str().empty())
-        res << ',';
-      res << key.tag();
+      if (!res.empty())
+        res += ',';
+      res += key.tag();
       auto pos = exifData_->findKey(key);
       if (pos == exifData_->end())
         continue;
@@ -1259,12 +1256,11 @@ std::string Converter::computeExifDigest(bool tiff) {
     }
   }
   MD5Final(digest, &context);
-  res << ';';
-  res << std::setw(2) << std::setfill('0') << std::hex << std::uppercase;
+  res += ';';
   for (const auto& i : digest) {
-    res << static_cast<int>(i);
+    res += stringFormat("{:02X}", i);
   }
-  return res.str();
+  return res;
 }
 #else
 std::string Converter::computeExifDigest(bool) {
diff --git a/src/datasets.cpp b/src/datasets.cpp
index 355dee7dfd..36bb719cf9 100644
--- a/src/datasets.cpp
+++ b/src/datasets.cpp
@@ -443,17 +443,13 @@ bool IptcDataSets::dataSetRepeatable(uint16_t number, uint16_t recordId) {
 }
 
 uint16_t IptcDataSets::dataSet(const std::string& dataSetName, uint16_t recordId) {
-  uint16_t dataSet = 0;
   if (int idx = dataSetIdx(dataSetName, recordId); idx != -1) {
     // dataSetIdx checks the range of recordId
-    dataSet = records_[recordId][idx].number_;
-  } else {
-    if (!isHex(dataSetName, 4, "0x"))
-      throw Error(ErrorCode::kerInvalidDataset, dataSetName);
-    std::istringstream is(dataSetName);
-    is >> std::hex >> dataSet;
+    return records_[recordId][idx].number_;
   }
-  return dataSet;
+  if (!isHex(dataSetName, 4, "0x"))
+    throw Error(ErrorCode::kerInvalidDataset, dataSetName);
+  return std::stoi(dataSetName, nullptr, 16);
 }
 
 std::string IptcDataSets::recordName(uint16_t recordId) {
@@ -480,8 +476,7 @@ uint16_t IptcDataSets::recordId(const std::string& recordName) {
   if (i == 0) {
     if (!isHex(recordName, 4, "0x"))
       throw Error(ErrorCode::kerInvalidRecord, recordName);
-    std::istringstream is(recordName);
-    is >> std::hex >> i;
+    i = std::stoi(recordName, nullptr, 16);
   }
   return i;
 }
diff --git a/src/futils.cpp b/src/futils.cpp
index 25796c98f1..159d8ea089 100644
--- a/src/futils.cpp
+++ b/src/futils.cpp
@@ -5,6 +5,7 @@
 
 #include "config.h"
 #include "enforce.hpp"
+#include "image_int.hpp"
 #include "utils.hpp"
 
 // + standard includes
@@ -240,7 +241,7 @@ bool fileExists(const std::string& path) {
 
 std::string strError() {
   int error = errno;
-  std::ostringstream os;
+  std::string os;
 #ifdef EXV_HAVE_STRERROR_R
   const size_t n = 1024;
 #ifdef EXV_STRERROR_R_CHAR_P
@@ -251,17 +252,16 @@ std::string strError() {
   const int ret = strerror_r(error, buf, n);
   Internal::enforce(ret != ERANGE, Exiv2::ErrorCode::kerCallFailed);
 #endif
-  os << buf;
+  os = buf;
   // Issue# 908.
   // report strerror() if strerror_r() returns empty
-  if (!buf[0]) {
-    os << strerror(error);
+  if (os.empty()) {
+    os = std::strerror(error);
   }
 #else
-  os << std::strerror(error);
+  os = std::strerror(error);
 #endif
-  os << " (errno = " << error << ")";
-  return os.str();
+  return stringFormat("{} (errno = {})", os, error);
 }  // strError
 
 void Uri::Decode(Uri& uri) {
diff --git a/src/tags.cpp b/src/tags.cpp
index e84d5164a8..293cab2d4c 100644
--- a/src/tags.cpp
+++ b/src/tags.cpp
@@ -5,6 +5,7 @@
 
 #include "error.hpp"
 #include "i18n.h"  // NLS support.
+#include "image_int.hpp"
 #include "tags_int.hpp"
 #include "types.hpp"
 
@@ -179,9 +180,7 @@ std::string ExifKey::Impl::tagName() const {
   if (tagInfo_ && tagInfo_->tag_ != 0xffff) {
     return tagInfo_->name_;
   }
-  std::ostringstream os;
-  os << "0x" << std::setw(4) << std::setfill('0') << std::right << std::hex << tag_;
-  return os.str();
+  return stringFormat("0x{:04x}", tag_);
 }
 
 void ExifKey::Impl::decomposeKey(const std::string& key) {
diff --git a/src/tags_int.cpp b/src/tags_int.cpp
index 0d305f4d17..71fb781c3d 100644
--- a/src/tags_int.cpp
+++ b/src/tags_int.cpp
@@ -2625,10 +2625,7 @@ uint16_t tagNumber(const std::string& tagName, IfdId ifdId) {
     return ti->tag_;
   if (!isHex(tagName, 4, "0x"))
     throw Error(ErrorCode::kerInvalidTag, tagName, ifdId);
-  std::istringstream is(tagName);
-  uint16_t tag = 0;
-  is >> std::hex >> tag;
-  return tag;
+  return std::stoi(tagName, nullptr, 16);
 }  // tagNumber
 
 std::ostream& printInt64(std::ostream& os, const Value& value, const ExifData*) {