Class LayerHashCalculator

LayerHashCalculator class

Hash Calculator for PSD Layers. It can be used to found equals or different layers in different PSD files

public class LayerHashCalculator

Constructors

Name	Description
LayerHashCalculator(Layer)	Initializes a new instance of the LayerHashCalculator class.

Methods

Name	Description
GetBlendingHash()	Gets the blending hash.
GetChannelsHash()	Gets the channels hash.
GetContentHash()	Gets the content hash.

Examples

The following code demonstrates the API for getting the unique hash for similar layers in different files.

[C#]

/// <summary>
/// Gets the name of the layer by.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="image">The image.</param>
/// <param name="name">The name.</param>
/// <returns></returns>
private static T GetLayerByName<T>(PsdImage image, string name) where T : Layer
{
    var layers = image.Layers;
    foreach (var layer in layers)
    {
        if (layer.Name == name)
        {
            return (T) layer;
        }
    }

    return null;
}

/// <summary>
/// Ares the not equal.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="expected">The expected.</param>
/// <param name="actual">The actual.</param>
/// <exception cref="System.Exception">Arguments must not be equal</exception>
public static void AreNotEqual<T>(T expected, T actual)
{
    if (expected != null && expected.Equals(actual))
    {
        throw new Exception("Arguments must not be equal");
    }
}

/// <summary>
/// Ares the equal.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="expected">The expected.</param>
/// <param name="actual">The actual.</param>
/// <exception cref="System.Exception">Arguments must be equal</exception>
public static void AreEqual<T>(T expected, T actual)
{
    if (expected != null && !expected.Equals(actual))
    {
        throw new Exception("Arguments must be equal");
    }
}

/// <summary>
/// Regulars the layer content hash test.
/// </summary>
/// <param name="fileName">Name of the file.</param>
public static void RegularLayerContentHashTest(string fileName)
{
    using (var im = (PsdImage) Image.Load(fileName))
    {
        var layers = new Layer[9];
        var hashers = new LayerHashCalculator[9];

        for (int i = 0; i < layers.Length; i++)
        {
            layers[i] = GetLayerByName<Layer>(im, string.Format("Layer {0}", i + 1));
            hashers[i] = new LayerHashCalculator(layers[i]);
        }

        AreNotEqual(hashers[0].GetChannelsHash(), hashers[1].GetChannelsHash());
        AreNotEqual(hashers[1].GetChannelsHash(), hashers[2].GetChannelsHash());
        AreNotEqual(hashers[0].GetChannelsHash(), hashers[2].GetChannelsHash());
        AreNotEqual(hashers[5].GetChannelsHash(), hashers[7].GetChannelsHash());
        AreNotEqual(hashers[0].GetChannelsHash(), hashers[8].GetChannelsHash());

        // These layers' hashes are equal
        AreEqual(hashers[0].GetChannelsHash(), hashers[3].GetChannelsHash());
        AreEqual(hashers[1].GetChannelsHash(), hashers[4].GetChannelsHash());
        AreEqual(hashers[0].GetChannelsHash(), hashers[6].GetChannelsHash());

        // Check the blending mode hash 
        AreEqual(hashers[0].GetBlendingHash(), hashers[3].GetBlendingHash());
        AreEqual(hashers[1].GetBlendingHash(), hashers[4].GetBlendingHash());
        AreNotEqual(hashers[0].GetBlendingHash(), hashers[6].GetBlendingHash());

        // But pointers are different
        AreNotEqual(layers[0], layers[3]);
        AreNotEqual(layers[1], layers[4]);
        AreNotEqual(layers[0], layers[6]);
    }
}

/// <summary>
/// Fills the layer content hash test.
/// </summary>
/// <param name="fileName">Name of the file.</param>
public static void FillLayerContentHashTest(string fileName)
{
    using (var im = (PsdImage) Image.Load(fileName))
    {
        var fillLayersNames = new string[] { "Color Fill", "Gradient Fill", "Pattern Fill" };

        var colorFillLayers = new Layer[4];
        var colorFillHashers = new LayerHashCalculator[4];

        for (int fillLayerIndex = 0; fillLayerIndex < fillLayersNames.Length; fillLayerIndex++)
        {
            for (int i = 0; i < 2; i++)
            {
                var index = 0 + i * 2;
                colorFillLayers[index] = GetLayerByName<Layer>(im,
                    string.Format("{0} 1_{1}", fillLayersNames[fillLayerIndex], i + 1));
                colorFillHashers[index] = new LayerHashCalculator(colorFillLayers[index]);
                index = 1 + i * 2;
                colorFillLayers[index] = GetLayerByName<Layer>(im,
                    string.Format("{0} 2_{1}", fillLayersNames[fillLayerIndex], i + 1));
                colorFillHashers[index] = new LayerHashCalculator(colorFillLayers[index]);
            }

            // Similar layers are always in the one index
            AreEqual(colorFillHashers[0].GetContentHash(), colorFillHashers[2].GetContentHash());
            AreEqual(colorFillHashers[1].GetContentHash(), colorFillHashers[3].GetContentHash());
            AreNotEqual(colorFillHashers[0].GetContentHash(), colorFillHashers[1].GetContentHash());
        }
    }
}

/// <summary>
/// Smarts the object layer content hash test.
/// </summary>
/// <param name="fileName">Name of the file.</param>
public static void SmartObjectLayerContentHashTest(string fileName)
{
    using (var im = (PsdImage) Image.Load(fileName))
    {
        var smartObjects = new Layer[]
        {
            GetLayerByName<Layer>(im, "Regular1_1"),
            GetLayerByName<Layer>(im, "Regular1_2"),
            GetLayerByName<Layer>(im, "Regular2_1"),
            GetLayerByName<Layer>(im, "Regular2_2"),
            GetLayerByName<Layer>(im, "Smart1_1"),
            GetLayerByName<Layer>(im, "Smart1_2"),
            GetLayerByName<Layer>(im, "Smart2_1"),
            GetLayerByName<Layer>(im, "Smart2_2"),
        };

        var hashers = new LayerHashCalculator[smartObjects.Length];

        for (int i = 0; i < smartObjects.Length; i++)
        {
            hashers[i] = new LayerHashCalculator(smartObjects[i]);
        }

        // Channel data is equal for Layer and Createad from them Smart Objects.
        AreEqual(hashers[0].GetChannelsHash(), hashers[2].GetChannelsHash());
        AreEqual(hashers[0].GetChannelsHash(), hashers[4].GetChannelsHash());

        // Content Hash is different, because Smart Object uses other data as content
        AreNotEqual(hashers[0].GetContentHash(), hashers[4].GetContentHash());

        // But blending hash is similar. Both layers - smart and regular have Normal Blend mode and opacity 255
        AreEqual(hashers[0].GetBlendingHash(), hashers[4].GetBlendingHash());

        // Channel data is equal for Layer and Createad from them Smart Objects.
        AreEqual(hashers[1].GetChannelsHash(), hashers[3].GetChannelsHash());
        AreEqual(hashers[1].GetChannelsHash(), hashers[5].GetChannelsHash());

        // Content Hash is different, because Smart Object uses other data as content
        AreNotEqual(hashers[1].GetContentHash(), hashers[5].GetContentHash());
        // But blending hash is similar. Both layers - smart and regular have Normal Blend mode and opacity 255
        AreEqual(hashers[1].GetBlendingHash(), hashers[5].GetBlendingHash());

        AreNotEqual(hashers[0].GetChannelsHash(), hashers[1].GetChannelsHash());
        AreNotEqual(hashers[2].GetChannelsHash(), hashers[3].GetChannelsHash());
        AreNotEqual(hashers[4].GetChannelsHash(), hashers[5].GetChannelsHash());
    }
}

/// <summary>
/// Adjustments the layers content hash test.
/// </summary>
/// <param name="fileName">Name of the file.</param>
public static void AdjustmentLayersContentHashTest(string fileName)
{
    using (var im = (PsdImage) Image.Load(fileName))
    {
        var adjustments = new Layer[]
        {
            GetLayerByName<Layer>(im, "Brightness/Contrast 1"),
            GetLayerByName<Layer>(im, "Levels 1"),
            GetLayerByName<Layer>(im, "Curves 1"),
            GetLayerByName<Layer>(im, "Exposure 1"),
            GetLayerByName<Layer>(im, "Vibrance 1"),
            GetLayerByName<Layer>(im, "Hue/Saturation 1"),
            GetLayerByName<Layer>(im, "Color Balance 1"),
            GetLayerByName<Layer>(im, "Black & White 1"),
            GetLayerByName<Layer>(im, "Photo Filter 1"),
            GetLayerByName<Layer>(im, "Channel Mixer 1"),
            GetLayerByName<Layer>(im, "Invert 1"),
            GetLayerByName<Layer>(im, "Posterize 1"),
        };

        var length = adjustments.Length;
        var hashers = new LayerHashCalculator[length];

        for (int i = 0; i < length; i++)
        {
            hashers[i] = new LayerHashCalculator(adjustments[i]);
        }

        // All hashes must be different
        for (int i = 0; i < length; i++)
        {
            for (int j = i + 1; j < length; j++)
            {
                AreNotEqual(hashers[i].GetContentHash(), hashers[j].GetContentHash());
                AreEqual(hashers[i].GetBlendingHash(), hashers[j].GetBlendingHash());
            }
        }
    }
}

/// <summary>
/// Texts the layers content hash test.
/// </summary>
/// <param name="fileName">Name of the file.</param>
public static void TextLayersContentHashTest(string fileName)
{
    using (var im = (PsdImage) Image.Load(fileName))
    {
        var textLayers1 = new TextLayer[]
        {
            GetLayerByName<TextLayer>(im, "Text 1"),
            GetLayerByName<TextLayer>(im, "Text 1 Similar"),
            GetLayerByName<TextLayer>(im, "Text 1 Changed"),
        };

        var textLayers2 = new TextLayer[]
        {
            GetLayerByName<TextLayer>(im, "Text 2"),
            GetLayerByName<TextLayer>(im, "Text 2 Similar"),
            GetLayerByName<TextLayer>(im, "Text 2 Changed 1"),
            GetLayerByName<TextLayer>(im, "Text 2 Changed 2"),
            GetLayerByName<TextLayer>(im, "Text 2 Rotated"),
        };

        var textHashers1 = new LayerHashCalculator[textLayers1.Length];
        var textHashers2 = new LayerHashCalculator[textLayers2.Length];

        for (int i = 0; i < textLayers1.Length; i++)
        {
            textHashers1[i] = new LayerHashCalculator(textLayers1[i]);
        }

        for (int i = 0; i < textLayers2.Length; i++)
        {
            textHashers2[i] = new LayerHashCalculator(textLayers2[i]);
        }

        AreEqual(textHashers1[0].GetContentHash(), textHashers1[1].GetContentHash());
        AreNotEqual(textHashers1[0].GetContentHash(), textHashers1[2].GetContentHash());

        AreEqual(textHashers2[0].GetContentHash(), textHashers2[1].GetContentHash());

        AreNotEqual(textHashers2[0].GetContentHash(), textHashers2[2].GetContentHash());
        AreNotEqual(textHashers2[0].GetContentHash(), textHashers2[3].GetContentHash());

        // Transformation matrix is not used in hash calculation. You should additionaly check it
        AreEqual(textHashers2[0].GetContentHash(), textHashers2[4].GetContentHash());

        // In this case we have a rotation in matrix
        AreNotEqual(textLayers2[0].TransformMatrix, textLayers2[4].TransformMatrix);
        // In this case we have only translation (Text Layer Shifted below)
        AreNotEqual(textLayers2[0].TransformMatrix, textLayers2[1].TransformMatrix);
    }
}

/// <summary>
/// Groups the layer content hash test.
/// </summary>
/// <param name="fileName">Name of the file.</param>
public static void GroupLayerContentHashTest(string fileName)
{
    using (var im = (PsdImage) Image.Load(fileName))
    {
        var fillLayersNames = new string[] { "Color Fill", "Gradient Fill", "Pattern Fill" };

        var groupLayers = new Layer[2];
        var groupLayersHashers = new LayerHashCalculator[2];

        groupLayers[0] = GetLayerByName<Layer>(im, "Fill");
        groupLayers[1] = GetLayerByName<Layer>(im, "Fill copy");

        for (int i = 0; i < groupLayers.Length; i++)
        {
            groupLayersHashers[i] = new LayerHashCalculator(groupLayers[i]);
        }

        // Group Layer Hash is calculated from layerss inside it
        AreEqual(groupLayersHashers[0].GetContentHash(), groupLayersHashers[1].GetContentHash());
        AreNotEqual(groupLayers[0], groupLayers[1]);
    }
}

/// <summary>
/// Regulars the layer content from different files hash test.
/// </summary>
/// <param name="fileName">Name of the file.</param>
public static void RegularLayerContentFromDifferentFilesHashTest(string fileName, string outputFile)
{
    using (var im = (PsdImage) Image.Load(fileName, new PsdLoadOptions() { ReadOnlyMode = true }))
    {
        im.Save(outputFile);
    }

    using (var im = (PsdImage) Image.Load(fileName))
    {
        using (var imCopied = (PsdImage) Image.Load(outputFile))
        {
            for (int i = 0; i < im.Layers.Length; i++)
            {
                var layer = im.Layers[i];
                var layer_copied = imCopied.Layers[i];
                var hashCalc = new LayerHashCalculator(layer);
                var hashCalc_copied = new LayerHashCalculator(layer_copied);

                // Layers have different pointers
                AreNotEqual(layer, layer_copied);

                // But hash of layers are equal
                AreEqual(hashCalc.GetChannelsHash(), hashCalc_copied.GetChannelsHash());
                AreEqual(hashCalc.GetContentHash(), hashCalc_copied.GetContentHash());
            }
        }
    }
    
    File.Delete(outputFile);
}

See Also

• namespace Aspose.PSD.FileFormats.Psd.Layers
• assembly Aspose.PSD