printing images (beta)

CHANGELOG.md

+## [1.2.0]
+* printing images (beta)
+  
+
 ## [1.1.3]
 * printCodeTable bug fixed
 * updated test print example 
 
+
 ## [1.1.2]
 * Better alignment
 
+
 ## [1.1.1]
 * Fixed columns alignment bug
 
+
 ## [1.1.0]
 * Added code page support
 
+
 ## [1.0.2]
 * Send raw command(s)
 * Turn 90° clockwise rotation mode on/off

README.md

@@ -76,9 +76,20 @@ printer.printRow([
     ]);
 ```
 
+Print image:
+
+```dart
+import 'dart:io';
+import 'package:image/image.dart';
+
+const String filename = './logo.png';
+final Image image = decodeImage(File(filename).readAsBytesSync());
+printer.printImage(image);
+```
+
 ## TODO
 * ~~Add raw print function~~
-* Print images
+* ~~Print images~~
 * Print barcodes
 * Print QR codes
 * ~~Turn 90° clockwise rotation mode on/off~~

example/example.dart

+import 'dart:io';
 import 'package:esc_pos_printer/esc_pos_printer.dart';
+import 'package:image/image.dart';
 
 void main() {
   // To discover existing printers in your subnet, consider using
   // ping_discover_network package (https://pub.dev/packages/ping_discover_network).
   // Note that most of ESC/POS printers by default listen on port 9100.
   Printer.connect('192.168.0.123', port: 9100).then((printer) {
-    printer.println('Regular: aA bB cC dD eE fF gG hH iI jJ kK lL mM nN oO pP qQ rR sS tT uU vV wW xX yY zZ');
+    printer.println(
+        'Regular: aA bB cC dD eE fF gG hH iI jJ kK lL mM nN oO pP qQ rR sS tT uU vV wW xX yY zZ');
     printer.println('Special 1: àÀ èÈ éÉ ûÛ üÜ çÇ ôÔ',
         styles: PosStyles(codeTable: PosCodeTable.westEur));
     printer.println('Special 2: blåbærgrød',
@@ -43,6 +46,10 @@ void main() {
           width: PosTextSize.size2,
         ));
 
+    const String filename = './logo.png';
+    final Image image = decodeImage(File(filename).readAsBytesSync());
+    printer.printImage(image);
+
     printer.cut();
     printer.disconnect();
   });

lib/src/commands.dart

@@ -44,3 +44,6 @@ const cPos = '$esc\$'; // Set absolute print position [nL] [nH]
 // Print
 const cFeedN = '${esc}d'; // Print and feed n lines [N]
 const cReverseFeedN = '${esc}e'; // Print and reverse feed n lines [N]
+
+// Bit Image
+const cImgPrint = '${gs}v0'; // Print raster bit image [obsolete command]

lib/src/printer.dart

@@ -10,6 +10,7 @@ import 'dart:convert';
 import 'dart:io';
 import 'dart:typed_data';
 import 'package:hex/hex.dart';
+import 'package:image/image.dart';
 import 'commands.dart';
 import 'enums.dart';
 import 'pos_column.dart';
@@ -281,4 +282,79 @@ class Printer {
       _socket.write(cCutFull);
     }
   }
+
+  /// Generate multiple bytes for a number: In lower and higher parts, or more parts as needed.
+  ///
+  /// [value] Input number
+  /// [bytesNb] The number of bytes to output (1 - 4)
+  List<int> _intLowHigh(int value, int bytesNb) {
+    final dynamic maxInput = 256 << (bytesNb * 8) - 1;
+
+    if (bytesNb < 1 || bytesNb > 4) {
+      throw Exception('Can only output 1-4 bytes');
+    }
+    if (value < 0 || value > maxInput) {
+      throw Exception(
+          'Number too large. Can only output up to $maxInput in $bytesNb bytes');
+    }
+
+    final List<int> res = <int>[];
+    int buf = value;
+    for (int i = 0; i < bytesNb; ++i) {
+      res.add(buf % 256);
+      buf = buf ~/ 256;
+    }
+    return res;
+  }
+
+  List<int> _convert1bit(List<int> bytes) {
+    final List<int> res = [];
+    for (int i = 0; i < bytes.length; i += 8) {
+      res.add(bytes[i]);
+    }
+    return res;
+  }
+
+  /// Print image
+  ///
+  /// [image] is an instanse of class from [Image library](https://pub.dev/packages/image)
+  void printImage(Image image) {
+    const bool highDensityHorizontal = true;
+    const bool highDensityVertical = true;
+
+    final int widthPx = image.width;
+    final int heightPx = image.height;
+
+    final int widthBytes = (widthPx + 7) ~/ 8;
+    const int densityByte =
+        (highDensityVertical ? 0 : 1) + (highDensityHorizontal ? 0 : 2);
+
+    final List<int> header = List.from(cImgPrint.codeUnits);
+    header.add(densityByte);
+    header.addAll(_intLowHigh(widthBytes, 2));
+    header.addAll(_intLowHigh(heightPx, 2));
+
+    final xL = header[4];
+    final xH = header[5];
+
+    final newWidth = (xL + xH * 256) * 8;
+    final Image imgResized =
+        copyResize(image, width: newWidth, height: image.height);
+
+    final Image imgGreyscale = grayscale(imgResized);
+    final Image imgInvert = invert(imgGreyscale);
+
+    final bytes = imgInvert.getBytes(format: Format.luminance);
+
+    final res = _convert1bit(bytes);
+
+    // print('img w * h (src): $widthPx * $heightPx');
+    // print('img w * h (new): ${imgResized.width} * ${imgResized.height}');
+    // print('source bytes: ${bytes.length}');
+    // print('= target bytes: ${(xL + xH * 256) * (header[6] + header[7] * 256)}');
+    // print('= to print bytes: ${res.length}');
+    // print(header);
+
+    sendRaw(List.from(header)..addAll(res));
+  }
 }

pubspec.yaml

 name: esc_pos_printer
 description: The library allows to print receipts using a ESC/POS (usually thermal) network printer. It can be used in Flutter or Dart projects. In Flutter, both Android and iOS are supported.
-version: 1.1.3
+version: 1.2.0
 author: Andrey Ushakov <flutter@tablemi.com>
 homepage: https://github.com/andrey-ushakov/esc_pos_printer
 
@@ -11,6 +11,7 @@ dependencies:
   flutter:
     sdk: flutter
   hex: ^0.1.2
+  image: ^2.1.4
 
 dev_dependencies:
   flutter_test: