Selection cropping in the Blazor Image Editor Component

19 Jul 20235 minutes to read

The cropping feature in the Blazor Image Editor allows you to select and crop specific regions of an image. It offers different selection options, including custom shapes, squares, circles, and various aspect ratios such as 3:2, 4:3, 5:4, 7:5, and 16:9.

To perform a selection, you can use the SelectAsync method, which allows you to define the desired selection area within the image. Once the selection is made, you can then use the CropAsync method to crop the image based on the selected region. This enables you to extract and focus on specific parts of the image while discarding the rest.

Insert custom / square / circle region

The SelectAsync method allows to perform selection based on the type of selection. Here, the SelectAsync method is used to perform the selection as custom, circle, or square. The selection region can also be customized using the select method based on the parameters below.

type - Specify the type of selection

startX - Specify the x-coordinate of the selection region’s starting point

startY - Specify the y-coordinate of the selection region’s starting point

width - Specify the width of the selection region

height - Specify the height of the selection region

Here is an example of square selection using the SelectAsync method.

@using Syncfusion.Blazor.ImageEditor
@using Syncfusion.Blazor.Buttons

<div style="padding-bottom: 15px">
    <SfButton OnClick="SelectAsync">Select</SfButton>
</div>
<SfImageEditor @ref="ImageEditor" Toolbar="customToolbarItem" Height="400">
    <ImageEditorEvents Created="OpenAsync"></ImageEditorEvents>
</SfImageEditor> 

@code {
    SfImageEditor ImageEditor; 
    private List<ImageEditorToolbarItemModel> customToolbarItem = new List<ImageEditorToolbarItemModel>() { }; 

    private async void OpenAsync() 
    { 
        await ImageEditor.OpenAsync("nature.png"); 
    }

    private async void SelectAsync()
    {
        await ImageEditor.SelectAsync("Square");
    }
}

Blazor Image Editor with Square select

Insert selection based on aspect ratio

The SelectAsync method is used to perform the selection with the various aspect ratios such as 3:2, 4:3, 5:4, 7:5, and 16:9. The selection region can also be customized using the SelectAsync method based on the parameters below.

type - Specify the type of selection

startX - Specify the x-coordinate of the selection region’s starting point

startY - Specify the y-coordinate of the selection region’s starting point

Here is an example of ratio selection using the SelectAsync method.

@using Syncfusion.Blazor.ImageEditor
@using Syncfusion.Blazor.Buttons

<div style="padding-bottom: 15px">
    <SfButton OnClick="SelectAsync">Select</SfButton>
</div>
<SfImageEditor @ref="ImageEditor" Toolbar="customToolbarItem" Height="400">
    <ImageEditorEvents Created="OpenAsync"></ImageEditorEvents>
</SfImageEditor> 

@code {
    SfImageEditor ImageEditor; 
    private List<ImageEditorToolbarItemModel> customToolbarItem = new List<ImageEditorToolbarItemModel>() { }; 

    private async void OpenAsync() 
    { 
        await ImageEditor.OpenAsync("nature.png"); 
    }

    private async void SelectAsync()
    {
        await ImageEditor.SelectAsync("16:9");
    }
}

Blazor Image Editor with Ratio select

Resize selections

The selection region can be changed programmatically by using OnSelectionResizeStart and OnSelectionResizeEnd event. This event is activated during resizing the selection using mouse, and it allows for alterations to the selection region by adjusting the specified properties.

The SelectionChangeEventArgs is used in these events to customize the selection and it has the following parameters.

SelectionChangeEventArgs.Action - The type of action such as inserting or resizing

SelectionChangeEventArgs.Cancel - Specifies to cancel the selection.

SelectionChangeEventArgs.CurrentSelectionPoint - Represents all the details of the selection including its type, position, width, and height after the current action as CropSelectionSettings.

SelectionChangeEventArgs.PreviousSelectionPoint - Represents all the details of the selection including its type, position, width, and height before this current action as CropSelectionSettings

Here is an example of changing the selection region using the SelectionChangeEventArgs event.

@using Syncfusion.Blazor.ImageEditor

<SfImageEditor @ref="ImageEditor" Height="400" Toolbar="customToolbarItem">
    <ImageEditorEvents Created="OpenAsync" OnSelectionResizeStart="OnSelectionResizeStart"></ImageEditorEvents>
</SfImageEditor>

@code {
    SfImageEditor ImageEditor;
    private List<ImageEditorToolbarItemModel> customToolbarItem = new List<ImageEditorToolbarItemModel>()
    {
        new ImageEditorToolbarItemModel { Name = "Crop" },
        new ImageEditorToolbarItemModel { Name = "Reset" },
        new ImageEditorToolbarItemModel { Name = "Confirm" }
    };

    private async void OpenAsync()
    {
        await ImageEditor.OpenAsync("nature.png");
    }

    private void OnSelectionResizeStart(SelectionChangeEventArgs args)
    {
        if (args.CurrentSelectionSettings.Type == "Custom")
        {
            args.CurrentSelectionSettings.Height = 200;
        }
    }
}

Blazor Image Editor with Resize the custom selection

Crop an image

The CropAsync method allows cropping based on the selected region. Here is an example of cropping the selection region using the CropAsync method.

Here is an example of circle cropping using the SelectAsync and CropAsync method.

@using Syncfusion.Blazor.ImageEditor
@using Syncfusion.Blazor.Buttons

<div style="padding-bottom: 15px">
    <SfButton OnClick="CropAsync">Crop</SfButton>
</div>
<SfImageEditor @ref="ImageEditor" Toolbar="customToolbarItem" Height="400">
    <ImageEditorEvents Created="OpenAsync"></ImageEditorEvents>
</SfImageEditor> 

@code {
    SfImageEditor ImageEditor; 
    private List<ImageEditorToolbarItemModel> customToolbarItem = new List<ImageEditorToolbarItemModel>() { }; 

    private async void OpenAsync() 
    { 
        await ImageEditor.OpenAsync("nature.png"); 
    }

    private async void CropAsync()
    {
        await ImageEditor.SelectAsync("Circle");
        await ImageEditor.CropAsync();
    }
}

Blazor Image Editor with Crop an image

Cropping event

The Cropping event is triggered when performing cropping on the image. This event is passed an object that contains information about the cropping event, such as the start and end point of the selection region. And this event uses CropEventArgs to handle the cropping action.

The parameter available in the Cropping event is,

  • CropEventArgs.StartPoint – The x and y coordinates of a start point as ImageEditorPoint of the selection region.

  • CropEventArgs.EndPoint - The x and y coordinates of an end point as ImageEditorPoint of the selection region.

  • CropEventArgs.Cancel - To cancel the cropping action.