/// <summary>
/// Randomly distorts the specified image that contains a single character.
/// </summary>
/// <param name="image">The image to distort.</param>
/// <param name="width">The sample width, in pixels.</param>
/// <param name="height">The sample height, in pixels.</param>
/// <param name="shift">The value that indicates whether the bitmap should be shifted randomly.</param>
/// <param name="rotate">The value that indicates whether the bitmap should be rotated randomly.</param>
/// <param name="scale">The value that indicates whether the bitmap should be scale randomly.</param>
/// <param name="crop">The value that indicates whether the bitmap should be cropped randomly.</param>
/// <returns>
/// The sequence of <see cref="Imaging.Image"/> objects that contains the distorted images.
/// </returns>
public IEnumerable <Genix.Imaging.Image> Distort(
Genix.Imaging.Image image,
int width,
int height,
bool shift,
bool rotate,
bool scale,
bool crop)
{
if (image == null)
{
throw new ArgumentNullException(nameof(image));
}
if (image.BitsPerPixel == 8)
{
image.OtsuNormalizeBackground(image);
}
if (!image.IsAllWhite())
{
// rotate image randomly
if (rotate)
{
double angle = (width > 0 ? 18 : 3) * this.normalDistribution.Generate();
image.Rotate(image, angle, BorderType.BorderConst, image.WhiteColor);
}
// reduce image size to black area if bigger than requested
////image = image.CropBlackArea(1, 1);
if ((width > 0 && image.Width > width) || image.Height > height)
{
Rectangle blackArea = image.BlackArea();
if (!blackArea.IsEmpty && blackArea != image.Bounds)
{
blackArea.Inflate(1, 1);
blackArea.Intersect(image.Bounds);
if (blackArea.Height < height)
{
int dy = MinMax.Min((height - blackArea.Height) / 2, blackArea.Y, image.Height - blackArea.Bottom);
blackArea.Inflate(0, dy, 0, height - blackArea.Height - dy);
}
if (width > 0 && blackArea.Width < width)
{
int dx = MinMax.Min((width - blackArea.Width) / 2, blackArea.X, image.Width - blackArea.Right);
blackArea.Inflate(dx, 0, width - blackArea.Width - dx, 0);
}
blackArea.Intersect(image.Bounds);
if (blackArea != image.Bounds)
{
image = image.Crop(blackArea);
}
}
}
// scale down if bigger than needed
if (width > 0)
{
if (image.Width > width || image.Height > height)
{
double horizontalFactor = (double)width / image.Width;
double verticalFactor = (double)height / image.Height;
double scaleFactor = Math.Min(horizontalFactor, verticalFactor);
image.Scale(image, scaleFactor, new ScalingOptions());
}
}
else
{
if (image.Height > height)
{
double scaleFactor = (double)height / image.Height;
image.Scale(image, scaleFactor, new ScalingOptions());
}
}
// scale down image randomly
if (scale)
{
if (width > 0)
{
int newWidth = image.Width - Math.Abs(this.Random(-width / 4, width / 4));
if (newWidth <= 0)
{
newWidth = 1;
}
int newHeight = image.Height - Math.Abs(this.Random(-height / 4, height / 4));
if (newHeight <= 0)
{
newHeight = 1;
}
image.ScaleToSize(image, newWidth, newHeight, new ScalingOptions());
}
else
{
int newWidth = image.Width + this.Random(-image.Width / 10, image.Width / 10);
if (newWidth <= 0)
{
newWidth = 1;
}
int newHeight = image.Height - Math.Abs(this.Random(-height / 4, height / 4));
if (newHeight <= 0)
{
newHeight = 1;
}
image.ScaleToSize(image, newWidth, newHeight, new ScalingOptions());
double angle = 0.5 * this.normalDistribution.Generate();
image = image.Inflate(image.Height, 0, image.Height, 0, BorderType.BorderConst, image.WhiteColor);
image = image.Shear(angle);
Rectangle blackArea = image.BlackArea();
int left = Math.Max(blackArea.Left - 1, 0);
int right = Math.Min(blackArea.Right + 1, image.Width);
image = image.Crop(left, 0, right - left, image.Height);
}
}
}
// increase image size to fit the requested size
if (width > 0)
{
if (image.Width < width || image.Height < height)
{
int dx = width - image.Width;
int dy = height - image.Height;
int offsetx = dx / 2;
int offsety = dy / 2;
if (shift)
{
offsetx = this.Random(0, dx);
offsety = this.Random(0, dy);
}
image = image.Inflate(offsetx, offsety, dx - offsetx, dy - offsety, BorderType.BorderConst, image.WhiteColor);
}
}
else
{
// pad with empty space on the right to reduce width granularity
int newWidth = ((image.Width + 15) / 16) * 16;
// increase image size to fit the requested size
if (image.Width < newWidth || image.Height < height)
{
int dx = newWidth - image.Width;
int dy = height - image.Height;
int offsetx = dx / 2;
int offsety = dy / 2;
if (shift)
{
offsetx = this.Random(0, dx);
offsety = this.Random(0, dy);
}
image = image.Inflate(offsetx, offsety, dx - offsetx, dy - offsety, BorderType.BorderConst, image.WhiteColor);
}
}
yield return(image);
if (crop)
{
int oldWidth = image.Width;
int oldHeight = image.Height;
int inflatex = image.Width / 8;
int inflatey = image.Height / 8;
image = image.Inflate(inflatex, inflatey, inflatex, inflatey, BorderType.BorderConst, image.WhiteColor);
yield return(image.Crop(0, 0, oldWidth, oldHeight));
yield return(image.Crop(2 * inflatex, 0, oldWidth, oldHeight));
yield return(image.Crop(0, 2 * inflatey, oldWidth, oldHeight));
yield return(image.Crop(2 * inflatex, 2 * inflatey, oldWidth, oldHeight));
}
}