How to convert camera image to image? - flutter

Question

I want to convert camera image from function startImageStream of camera plugin in Flutter to Image to crop that image but I only find the way to convert to FirebaseVisionImage.

Answer 1

Edit For Color Image
if I understand you clear. You are trying to covnert YUV420 format. The following is code snippet from: https://github.com/flutter/flutter/issues/26348
const shift = (0xFF << 24);
Future<Image> convertYUV420toImageColor(CameraImage image) async {
try {
final int width = image.width;
final int height = image.height;
final int uvRowStride = image.planes[1].bytesPerRow;
final int uvPixelStride = image.planes[1].bytesPerPixel;
print("uvRowStride: " + uvRowStride.toString());
print("uvPixelStride: " + uvPixelStride.toString());
// imgLib -> Image package from https://pub.dartlang.org/packages/image
var img = imglib.Image(width, height); // Create Image buffer
// Fill image buffer with plane[0] from YUV420_888
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
final int uvIndex = uvPixelStride * (x / 2).floor() + uvRowStride * (y / 2).floor();
final int index = y * width + x;
final yp = image.planes[0].bytes[index];
final up = image.planes[1].bytes[uvIndex];
final vp = image.planes[2].bytes[uvIndex];
// Calculate pixel color
int r = (yp + vp * 1436 / 1024 - 179).round().clamp(0, 255);
int g = (yp - up * 46549 / 131072 + 44 - vp * 93604 / 131072 + 91).round().clamp(0, 255);
int b = (yp + up * 1814 / 1024 - 227).round().clamp(0, 255);
// color: 0x FF FF FF FF
// A B G R
img.data[index] = shift | (b << 16) | (g << 8) | r;
}
}
imglib.PngEncoder pngEncoder = new imglib.PngEncoder(level: 0, filter: 0);
List<int> png = pngEncoder.encodeImage(img);
muteYUVProcessing = false;
return Image.memory(png);
} catch (e) {
print(">>>>>>>>>>>> ERROR:" + e.toString());
}
return null;
}

Answer 2

I found, sometimes planes[0] bytes per row is not same as width. In that case, you should do something like the code below.
static image_lib.Image convertYUV420ToImage(CameraImage cameraImage) {
final width = cameraImage.width;
final height = cameraImage.height;
final yRowStride = cameraImage.planes[0].bytesPerRow;
final uvRowStride = cameraImage.planes[1].bytesPerRow;
final uvPixelStride = cameraImage.planes[1].bytesPerPixel!;
final image = image_lib.Image(width, height);
for (var w = 0; w < width; w++) {
for (var h = 0; h < height; h++) {
final uvIndex =
uvPixelStride * (w / 2).floor() + uvRowStride * (h / 2).floor();
final index = h * width + w;
final yIndex = h * yRowStride + w;
final y = cameraImage.planes[0].bytes[yIndex];
final u = cameraImage.planes[1].bytes[uvIndex];
final v = cameraImage.planes[2].bytes[uvIndex];
image.data[index] = yuv2rgb(y, u, v);
}
}
return image;
}
static int yuv2rgb(int y, int u, int v) {
// Convert yuv pixel to rgb
var r = (y + v * 1436 / 1024 - 179).round();
var g = (y - u * 46549 / 131072 + 44 - v * 93604 / 131072 + 91).round();
var b = (y + u * 1814 / 1024 - 227).round();
// Clipping RGB values to be inside boundaries [ 0 , 255 ]
r = r.clamp(0, 255);
g = g.clamp(0, 255);
b = b.clamp(0, 255);
return 0xff000000 |
((b << 16) & 0xff0000) |
((g << 8) & 0xff00) |
(r & 0xff);
}