/// <summary>
/// Saves the DigitImageCollection to an image and label file that matches the format of the Mnist dataset files.
/// </summary>
public void SaveToFile(string imagesFile, string labelsFile)
{
//Create file streams and binary writers for the images and labels.
using (FileStream imagesFileStream = new FileStream(imagesFile, FileMode.OpenOrCreate, FileAccess.ReadWrite))
{
using (BinaryWriter imagesWriter = new BinaryWriter(imagesFileStream))
{
using (FileStream labelsFileStream = new FileStream(labelsFile, FileMode.OpenOrCreate, FileAccess.ReadWrite))
{
using (BinaryWriter labelsWriter = new BinaryWriter(labelsFileStream))
{
//The image file header should be in the following format
//[offset] [type] [value] [description]
//0000 32 bit integer 0x00000803(2051) magic number
//0004 32 bit integer 60000 number of images
//0008 32 bit integer 28 number of rows
//0012 32 bit integer 28 number of columns
//Write the "magic number" (not sure why we don't care about this)
imagesWriter.Write(0);
//Set the number of images in the collection
imagesWriter.Write(this.DigitImages.Length);
//Write the number of rows and columns (not sure why we don't care about these and I am not sure what they are supposed to correspond to)
imagesWriter.Write(0);
imagesWriter.Write(0);
//The label file header is similar, it has a magic number and the number of labels but no need for the rows or columns counts
//Writethe magic number
labelsWriter.Write(0);
//Set the number of labels
labelsWriter.Write(this.DigitImages.Length);
//Start writing pixel data
for (int imageIndex = 0; imageIndex < this.DigitImages.Length; imageIndex++)
{
DigitImage digitImage = this.DigitImages[imageIndex];
for (int y = 0; y < 28; y++)
{
for (int x = 0; x < 28; x++)
{
imagesWriter.Write(digitImage.Pixels[x][y]);
}
}
//Write the label for the image
labelsWriter.Write(digitImage.Label);
}
}
}
}
}
}
/// <summary>
/// Creates a DigitImageCollection from image and label files that are in the Mnist dataset format
/// </summary>
/// <param name="imageFile">A path to the file that contains the image data.</param>
/// <param name="labelFile">A path to thefile that contains labels for each image.</param>
/// <returns>An instance of DigitImageColleciton with all images and labels loaded from the files.</returns>
public static DigitImageCollection LoadMnistDataSet(string imageFile, string labelFile, int imageCount)
{
//Use this link for information about the file formats of the Mnist dataset - http://yann.lecun.com/exdb/mnist/
DigitImageCollection imageCollection = new DigitImageCollection();
//Create file streams and binary readers for the images and labels.
using (FileStream imagesFileStream = new FileStream(imageFile, FileMode.Open, FileAccess.Read))
{
using (BinaryReader imagesReader = new BinaryReader(imagesFileStream))
{
using (FileStream labelsFileStream = new FileStream(labelFile, FileMode.Open, FileAccess.Read))
{
using (BinaryReader labelsReader = new BinaryReader(labelsFileStream))
{
//The image file header should be in the following format
//[offset] [type] [value] [description]
//0000 32 bit integer 0x00000803(2051) magic number
//0004 32 bit integer 60000 number of images
//0008 32 bit integer 28 number of rows
//0012 32 bit integer 28 number of columns
//Read and discard the "magic number" (not sure why we don't care about this)
imagesReader.ReadInt32();
//Get the number of images in the dataset and initialize the image collections DigitImage array
int numberOfImages = imageCount; //I do not know why reading the number of images does not work, but it is way off
imagesReader.ReadInt32();
imageCollection.DigitImages = new DigitImage[numberOfImages];
//Read and discard the number of rows and columns (not sure why we don't care about these)
imagesReader.ReadInt32();
imagesReader.ReadInt32();
//The label file header is similar, it has a magic number and the number of labels but no need for the rows or columns counts
//Read and discard the magic number
labelsReader.ReadInt32();
//Get the number of labels
int numberOfLabels = imageCount; //I do not know why reading the number of labels does not work, but it is way off
labelsReader.ReadInt32();
//Make sure the number of labels and images match
if (numberOfImages != numberOfLabels)
{
throw new Exception("The number of images does not match the number of labels.");
}
//Start reading pixels and creating 28X28 DigitImages
for (int imageIndex = 0; imageIndex < numberOfImages; imageIndex++)
{
DigitImage digitImage = new DigitImage();
imageCollection.DigitImages[imageIndex] = digitImage;
for (int y = 0; y < 28; y++)
{
for (int x = 0; x < 28; x++)
{
digitImage.Pixels[x][y] = imagesReader.ReadByte();
}
}
//Get the label for the image
digitImage.Label = labelsReader.ReadByte();
}
}
}
}
}
return(imageCollection);
}
