Flutter Custom Painter - missing offset in coefficient calculation - flutter

Question

first i transform my image file to dart:ui image. then i set sizes i will be using with this method
void setSizes() async {
imgOgSize =
Size(image.value!.width.toDouble(), image.value!.height.toDouble());
double wDiff = imgOgSize!.width - Get.width;
double hDiff = imgOgSize!.height - Get.height;
if (wDiff > hDiff) {
coef.value = imgOgSize!.width / Get.width;
canvasSize =
Size(imgOgSize!.width / coef.value, imgOgSize!.height / coef.value);
} else {
coef.value = imgOgSize!.height / Get.height;
canvasSize =
Size(imgOgSize!.width / coef.value, imgOgSize!.height / coef.value);
}
print(coef.value);
// canvasSize = Size(
// min(imgOgSize!.width, Get.width), min(imgOgSize!.height, Get.height));
}
my logic is finding size, that needs to be shrank more than the other and using it as a coefficient, because if i wanted to use fit: BoxFit.scaleDown i would not know what the coefficient would end up being.
the image is ready to be used on canvas, but i also need to get a list of points.
here is how i get the points
GestureDetector(
onPanDown: (detailData) {
controller.editor.value!.update(detailData.localPosition);
controller.canvasKey.currentContext!
.findRenderObject()!
.markNeedsPaint();
},
onPanUpdate: (detailData) {
controller.editor.value!.update(detailData.localPosition);
controller.canvasKey.currentContext!
.findRenderObject()!
.markNeedsPaint();
},
child: CustomPaint(
key: controller.canvasKey,
painter: controller.editor.value,
size: controller.canvasSize!,
),
)
now the overriden paint function looks like this with fullSize being false
void paint(Canvas canvas, Size size) {
final imageSize = Size(image.width.toDouble(), image.height.toDouble());
final src = Offset.zero & imageSize;
final dst = Offset.zero & size;
// canvas.drawImageRect(image, src, dst, Paint());
paintImage(
canvas: canvas,
rect: dst,
image: image,
// fit: BoxFit.scaleDown,
repeat: ImageRepeat.noRepeat,
scale: 1 / coef,
alignment: Alignment.center,
flipHorizontally: false,
filterQuality: FilterQuality.high,
);
for (Offset offset in points) {
if (fullSize) {
Offset of = Offset(offset.dx * coef, offset.dy * coef);
canvas.drawCircle(of, 10 * coef, painter);
} else {
canvas.drawCircle(offset, 10, painter);
}
}
}
result:
but now, when i want to export it with this function with image's original height and width, to have full quality picture (using imgOgSize instead of canvasSize)
Future<ui.Image> getImage() async {
final ui.PictureRecorder recorder = ui.PictureRecorder();
editor.value!.fullSize = true;
editor.value!.paint(Canvas(recorder), imgOgSize!);
editor.value!.fullSize = false;
final ui.Picture picture = recorder.endRecording();
ui.Image genImg = await picture.toImage(
imgOgSize!.width.toInt(), imgOgSize!.height.toInt());
// ui.Image genImg = await picture.toImage(canvasSize!.width.toInt(), canvasSize!.height.toInt());
final pngBytes = await genImg.toByteData(format: ui.ImageByteFormat.png);
final buffer = pngBytes!.buffer;
await File('/data/user/0/app/app_flutter/t1.png')
.delete();
await File('/data/user/0/app/app_flutter/t1.png')
.writeAsBytes(
buffer.asUint8List(pngBytes.offsetInBytes, pngBytes.lengthInBytes));
Get.find<HomeController>().imageViewPath.refresh();
Get.to(() => ImageView());
return await picture.toImage(
imgOgSize!.width.toInt(), imgOgSize!.height.toInt());
}
this is the exported .png result
am i calculating the coefficient wrong? or is there some offset im not taking in account? help please. i also can provide more code if something important is missing, let me know please.

Answer 1

edit: this answer works for phone orientation portrait, not landscape, which somehow still does not work. therefore i'm leaving the question open if someone can help.
i calculated the size wrong.
this is the correct setSizes()
void setSizes() {
imgOgSize =
Size(image.value!.width.toDouble(), image.value!.height.toDouble());
double wC = imgOgSize!.width / Get.width;
ouble hC = imgOgSize!.height / (Get.height - appBar.preferredSize.height);
if (wC > hC) {
coef.value = wC;
canvasSize =
Size(imgOgSize!.width / coef.value, imgOgSize!.height / coef.value);
} else {
coef.value = hC;
canvasSize =
Size(imgOgSize!.width / coef.value, imgOgSize!.height / coef.value);
}
print(coef.value);
// canvasSize = Size(
// min(imgOgSize!.width, Get.width), min(imgOgSize!.height, Get.height));
}