如何在 dart flutter 中转换图像 dpi（每英寸点数）？

Question

该问题与各种图像（例如 jpeg 或 png ）格式的（打印）DPI 有关。

这个问题与屏幕 DPI 或各种 Android 设备的大小无关。 它也与在设备上以屏幕尺寸显示 Bitmap 无关。

Answer 1

这会将图像分辨率每英寸点数转换为 300。

Uint8List resultBytes = provider.bytes;
  print(resultBytes.toString());
  
  var dpi = 300;
  resultBytes[13] = 1;
  resultBytes[14] = (dpi >> 8);
  resultBytes[15] = (dpi & 0xff);
  resultBytes[16] = (dpi >> 8);
  resultBytes[17] = (dpi & 0xff);

  print(resultBytes.toString());

  String tempPath = (await getTemporaryDirectory()).path;
  String imgName = "IMG" + DateTime.now().microsecondsSinceEpoch.toString()+".jpg";
  File file = File('$tempPath/$imgName');
  await file.writeAsBytes(resultBytes);

  /**You will not be able to see the image in android local storage, so rewriting the file, using the code below will show you image in Pictures Directory of android storage. Note: ImageGallerySaver is plugin, just copy and paste the dependency and have a go.*/

  final result1 = ImageGallerySaver.saveFile(file.path);
  print(result1);