copyResize function

Image copyResize(Image src, { int? width, int? height, Interpolation interpolation = Interpolation.nearest, })

Returns a resized copy of the src Image. If height isn't specified, then it will be determined by the aspect ratio of src and width. If width isn't specified, then it will be determined by the aspect ratio of src and height.

Implementation

Image copyResize(Image src,
    {int? width,
    int? height,
    Interpolation interpolation = Interpolation.nearest}) {
  if (width == null && height == null) {
    throw ImageException('Invalid size');
  }

  // You can't interpolate index pixels
  if (src.hasPalette) {
    interpolation = Interpolation.nearest;
  }

  if (src.exif.imageIfd.hasOrientation && src.exif.imageIfd.orientation != 1) {
    src = bakeOrientation(src);
  }

  // this block sets [width] and [height] if null or negative.
  if (height == null || height <= 0) {
    height = (width! * (src.height / src.width)).round();
  }
  if (width == null || width <= 0) {
    width = (height * (src.width / src.height)).round();
  }

  if (width == src.width && height == src.height) {
    return src.clone();
  }

  final scaleX = Int32List(width);
  final dx = src.width / width;
  for (var x = 0; x < width; ++x) {
    scaleX[x] = (x * dx).toInt();
  }

  Image? firstFrame;
  final numFrames = src.numFrames;
  for (var i = 0; i < numFrames; ++i) {
    final frame = src.frames[i];
    final dst = Image.fromResized(frame,
        width: width, height: height, noAnimation: true);
    firstFrame?.addFrame(dst);
    firstFrame ??= dst;

    final dy = frame.height / height;
    final dx = frame.width / width;

    if (interpolation == Interpolation.average) {
      for (var y = 0; y < height; ++y) {
        final y1 = (y * dy).toInt();
        var y2 = ((y + 1) * dy).toInt();
        if (y2 == y1) {
          y2++;
        }

        for (var x = 0; x < width; ++x) {
          final x1 = (x * dx).toInt();
          var x2 = ((x + 1) * dx).toInt();
          if (x2 == x1) {
            x2++;
          }

          num r = 0;
          num g = 0;
          num b = 0;
          num a = 0;
          var np = 0;
          for (var sy = y1; sy < y2; ++sy) {
            for (var sx = x1; sx < x2; ++sx, ++np) {
              final s = frame.getPixel(sx, sy);
              r += s.r;
              g += s.g;
              b += s.b;
              a += s.a;
            }
          }
          dst.setPixel(x, y, dst.getColor(r / np, g / np, b / np, a / np));
        }
      }
    } else if (interpolation == Interpolation.nearest) {
      if (frame.hasPalette) {
        for (var y = 0; y < height; ++y) {
          final y2 = (y * dy).toInt();
          for (var x = 0; x < width; ++x) {
            dst.setPixelIndex(x, y, frame.getPixelIndex(scaleX[x], y2));
          }
        }
      } else {
        for (var y = 0; y < height; ++y) {
          final y2 = (y * dy).toInt();
          for (var x = 0; x < width; ++x) {
            dst.setPixel(x, y, frame.getPixel(scaleX[x], y2));
          }
        }
      }
    } else {
      // Copy the pixels from this image to the new image.
      for (var y = 0; y < height; ++y) {
        final y2 = y * dy;
        for (var x = 0; x < width; ++x) {
          final x2 = x * dx;
          dst.setPixel(x, y,
              frame.getPixelInterpolate(x2, y2, interpolation: interpolation));
        }
      }
    }
  }

  return firstFrame!;
}