Image QML Type

The following example shows the simplest usage of the Image type.

import QtQuick 2.0

Image {
    source: "pics/qtlogo.png"
}

When supported by the implementation of the underlying graphics API at run time, images can also be supplied in compressed texture files. The content must be a simple RGB(A) format 2D texture. Supported compression schemes are only limited by the underlying driver and GPU. The following container file formats are supported:

• PKM (since Qt 5.10)

• KTX (since Qt 5.11)

• ASTC (since Qt 5.13)

transform: [ Translate { y: -myImage.height }, Scale { yScale: -1 } ]

or

mirrorVertically: true

convert foo.png \( +clone -alpha Extract \) -channel RGB -compose Multiply -composite foo_pm.png

If the source URL indicates a non-existing local file or resource, the Image element attempts to auto-detect the file extension. If an existing file can be found by appending any of the supported image file extensions to the source URL, then that file will be loaded.

The file search attempts to look for compressed texture container file extensions first. If the search is unsuccessful, it attempts to search with the file extensions for the conventional image file types. For example:

// Assuming the "pics" directory contains the following files:
//   dog.jpg
//   cat.png
//   cat.pkm

Image {
    source: "pics/cat.png"     // loads cat.png
}

Image {
    source: "pics/dog"         // loads dog.jpg
}

Image {
    source: "pics/cat"         // normally loads cat.pkm, but if no OpenGL, loads cat.png instead.
}

This functionality facilitates deploying different image asset file types on different target platforms. This can be useful in order to tune application performance and adapt to different graphics hardware.

This functionality was introduced in Qt 5.11.

By default, locally available images are loaded immediately, and the user interface is blocked until loading is complete. If a large image is to be loaded, it may be preferable to load the image in a low priority thread, by enabling the asynchronous property.

If the image is obtained from a network rather than a local resource, it is automatically loaded asynchronously, and the progress and status properties are updated as appropriate.

Images are cached and shared internally, so if several Image items have the same source, only one copy of the image will be loaded.

Note: Images are often the greatest user of memory in QML user interfaces. It is recommended that images which do not form part of the user interface have their size bounded via the sourceSize property. This is especially important for content that is loaded from external sources or provided by the user.

See also Qt Quick Examples - Image Elements, QQuickImageProvider, QImageReader::setAutoDetectImageFormat()

[read-only] paintedWidth : real

These properties hold the size of the image that is actually painted. In most cases it is the same as width and height, but when using an Image.PreserveAspectFit or an Image.PreserveAspectCrop paintedWidth or paintedHeight can be smaller or larger than width and height of the Image item.

verticalAlignment : enumeration

Sets the horizontal and vertical alignment of the image. By default, the image is center aligned.

The valid values for horizontalAlignment are Image.AlignLeft, Image.AlignRight and Image.AlignHCenter. The valid values for verticalAlignment are Image.AlignTop, Image.AlignBottom and Image.AlignVCenter.

[read-only, since 5.14] frameCount : int

currentFrame is the frame that is currently visible. The default is 0. You can set it to a number between 0 and frameCount - 1 to display a different frame, if the image contains multiple frames.

frameCount is the number of frames in the image. Most images have only one frame.

This QML property was introduced in Qt 5.14.

Specifies that images on the local filesystem should be loaded asynchronously in a separate thread. The default value is false, causing the user interface thread to block while the image is loaded. Setting asynchronous to true is useful where maintaining a responsive user interface is more desirable than having images immediately visible.

Note that this property is only valid for images read from the local filesystem. Images loaded via a network resource (e.g. HTTP) are always loaded asynchronously.

This property holds whether the image should automatically apply image transformation metadata such as EXIF orientation.

By default, this property is set to false.

This property was introduced in Qt 5.5.

Specifies whether the image should be cached. The default value is true. Setting cache to false is useful when dealing with large images, to make sure that they aren't cached at the expense of small 'ui element' images.

Set this property to define what happens when the source image has a different size than the item.

• Image.Stretch - the image is scaled to fit

• Image.PreserveAspectFit - the image is scaled uniformly to fit without cropping

• Image.PreserveAspectCrop - the image is scaled uniformly to fill, cropping if necessary

• Image.Tile - the image is duplicated horizontally and vertically

• Image.TileVertically - the image is stretched horizontally and tiled vertically

• Image.TileHorizontally - the image is stretched vertically and tiled horizontally

• Image.Pad - the image is not transformed

	Stretch (default)   Sélectionnez Image { width: 130; height: 100 source: "qtlogo.png" }
	PreserveAspectFit   Sélectionnez Image { width: 130; height: 100 fillMode: Image.PreserveAspectFit source: "qtlogo.png" }
	PreserveAspectCrop   Sélectionnez Image { width: 130; height: 100 fillMode: Image.PreserveAspectCrop source: "qtlogo.png" clip: true }
	Tile   Sélectionnez Image { width: 120; height: 120 fillMode: Image.Tile horizontalAlignment: Image.AlignLeft verticalAlignment: Image.AlignTop source: "qtlogo.png" }
	TileVertically   Sélectionnez Image { width: 120; height: 120 fillMode: Image.TileVertically verticalAlignment: Image.AlignTop source: "qtlogo.png" }
	TileHorizontally   Sélectionnez Image { width: 120; height: 120 fillMode: Image.TileHorizontally verticalAlignment: Image.AlignLeft source: "qtlogo.png" }

Note that clip is false by default which means that the item might paint outside its bounding rectangle even if the fillMode is set to PreserveAspectCrop.

See Also▲

This property holds whether the image uses mipmap filtering when scaled or transformed.

Mipmap filtering gives better visual quality when scaling down compared to smooth, but it may come at a performance cost (both when initializing the image and during rendering).

By default, this property is set to false.

This property was introduced in Qt 5.3.

See Also▲

This property holds whether the image should be horizontally inverted (effectively displaying a mirrored image).

The default value is false.

This property holds whether the image should be vertically inverted (effectively displaying a mirrored image).

The default value is false.

This property was introduced in Qt 6.2.

This property holds the progress of image loading, from 0.0 (nothing loaded) to 1.0 (finished).

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This property holds whether the image is smoothly filtered when scaled or transformed. Smooth filtering gives better visual quality, but it may be slower on some hardware. If the image is displayed at its natural size, this property has no visual or performance effect.

By default, this property is set to true.

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Image can handle any image format supported by Qt, loaded from any URL scheme supported by Qt.

The URL may be absolute, or relative to the URL of the component.

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This property, if set, holds the rectangular region of the source image to be loaded.

The sourceClipRect works together with the sourceSize property to conserve system resources when only a portion of an image needs to be loaded.

Rectangle {
    width: ...
    height: ...

    Image {
       anchors.fill: parent
       source: "reallyBigImage.svg"
       sourceSize.width: 1024
       sourceSize.height: 1024
       sourceClipRect: Qt.rect(100, 100, 512, 512)
    }
}

In the above example, we conceptually scale the SVG graphic to 1024x1024 first, and then cut out a region of interest that is 512x512 pixels from a location 100 pixels from the top and left edges. Thus sourceSize determines the scale, but the actual output image is 512x512 pixels.

Some image formats are able to conserve CPU time by rendering only the specified region. Others will need to load the entire image first and then clip it to the specified region.

This property can be cleared to reload the entire image by setting sourceClipRect to undefined.

This property was introduced in Qt 5.15.

This property holds the scaled width and height of the full-frame image.

Unlike the width and height properties, which scale the painting of the image, this property sets the maximum number of pixels stored for the loaded image so that large images do not use more memory than necessary. For example, this ensures the image in memory is no larger than 1024x1024 pixels, regardless of the Image's width and height values:

Rectangle {
    width: ...
    height: ...

    Image {
       anchors.fill: parent
       source: "reallyBigImage.jpg"
       sourceSize.width: 1024
       sourceSize.height: 1024
    }
}

If the image's actual size is larger than the sourceSize, the image is scaled down. If only one dimension of the size is set to greater than 0, the other dimension is set in proportion to preserve the source image's aspect ratio. (The fillMode is independent of this.)

If both the sourceSize.width and sourceSize.height are set, the image will be scaled down to fit within the specified size (unless PreserveAspectCrop or PreserveAspectFit are used, then it will be scaled to match the optimal size for cropping/fitting), maintaining the image's aspect ratio. The actual size of the image after scaling is available via Item::implicitWidth and Item::implicitHeight.

If the source is an intrinsically scalable image (eg. SVG), this property determines the size of the loaded image regardless of intrinsic size. Avoid changing this property dynamically; rendering an SVG is slow compared to an image.

If the source is a non-scalable image (eg. JPEG), the loaded image will be no greater than this property specifies. For some formats (currently only JPEG), the whole image will never actually be loaded into memory.

If the sourceClipRect property is also set, sourceSize determines the scale, but it will be clipped to the size of the clip rectangle.

sourceSize can be cleared to the natural size of the image by setting sourceSize to undefined.

This property holds the status of image loading. It can be one of:

• Image.Null - no image has been set

• Image.Ready - the image has been loaded

• Image.Loading - the image is currently being loaded

• Image.Error - an error occurred while loading the image

Use this status to provide an update or respond to the status change in some way. For example, you could:

• Trigger a state change:

   

  Sélectionnez

  State { name: 'loaded'; when: image.status == Image.Ready }

• Implement an onStatusChanged signal handler:

   

  Sélectionnez

  Image {
      id: image
      onStatusChanged: if (image.status == Image.Ready) console.log('Loaded')
  }

• Bind to the status value:

   

  Sélectionnez

  Text { text: image.status == Image.Ready ? 'Loaded' : 'Not loaded' }

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