【Android】 a common image conversion operation library

Preface detail image format specification interface specifications ImageFormat enumeration class enumeration class FilterModeImageInfoYuvUtils class 2.1 Bitmap converted to other image formats 2.2 various formats of mutual transformation between image 2.3 various formats of image is transformed into Bitmap2.4 Image rotation and cropping operations of various formats 2.5 Images of various formats are rotated and cropped into relevant Bitmap2.6 Mirror flip operations of images of various formats 2.7 Zoom operations of images of various formats ImageUtilsNV21 image operations of I420 image operations

preface

In daily development, when it comes to Android Camera or image-related development, there are more or less contact with some image formats, and various operations will be involved between these different formats. Here, an image manipulation library is encapsulated by Google’s open source framework Libyuv. It involves the image conversion operation commonly used in Android.

Functional specifications

√ Support RGB_565, ARGB_8888, RGB24, I420, NV21 5 format image conversion operation

√ Support to convert Bitmap into the above five image formats

√ Convert images in the above format to Bitmap

√ Support rotation cropping operation between images in the above formats

√ Support zoom operation between images in the above formats

√ Support image mirroring operation between the above formats

√ The bottom layer relies on the libyuv framework, which is safe, stable and efficient

Image format Description

For instructions on image formats, see here: Common Image formats in Android

Interface specification

Common image format conversion library address:ImageUtils

ImageFormat enumeration class

This class is used to illustrate the format of data conversion currently supported, as follows:

enum class ImageFormat(var format: Int) {

    NV21(1),

    I420(2),

    RGB_565(3),

    RGB_888(4),

    ARGB_8888(5)

}

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For details on the above data formats, please refer to common Image formats in Android

Enumeration class FilterMode

This enumeration class describes the filter modes supported when scaling an image, as follows:

enum class FilterMode(var filter: Int) {

    FilterNone(0),

    FilterLinear(1),

    FilterBilinear(2),

    FilterBox(3)

}

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For a description of filtering modes, see filter.md

ImageInfo

This class is mainly used to assist image data rotation clipping, as follows:

class ImageInfo(

    val data: ByteArray,

    val dataFormat: ImageFormat,

    val width: Int.

    val height: Int.

    @RotateDegree val degree: Int = 0.

    val rect: Rect? = null.

    val targetFormat: ImageFormat,

    val priorityClip: Boolean = true

)

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The parameters are described as follows:

• data: Source image data
• dataFormat: Source image data format. See the supported formatsImageFormat
• width: Width of source image
• height: Height of the source image
• degree: The Angle to be rotated
• rect: Rectangle coordinates to be clippedRectfornullIs not clipped
• targetFormat: Image format after processing. See supported formatsImageFormat
• priorityClip: Uses priority tailoring. The default value istureThis parameter is very important. We’ll talk about it later

YuvUtils class

This class is the core class of the library

2.1 Bitmap is converted to other image formats

There are five main interfaces:

external fun bitmapToNV21(bitmap: Bitmap?).: ByteArray?

external fun bitmapToRgb565(bitmap: Bitmap?).: ByteArray?

external fun bitmapToRgb24(bitmap: Bitmap?).: ByteArray?

external fun bitmapToRgba(bitmap: Bitmap?).: ByteArray?

external fun bitmapToI420(bitmap: Bitmap?).: ByteArray?

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• About the parametersbitmap, currently only supportedRGB_565 和 RGBA_8888Two types of bitmap conversion

2.2 Conversion between images of various formats

external fun imageFormatConvert(

    data: ByteArray.

    width: Int.

    height: Int.

    @SupportFormat dataFormat: Int.

    @SupportFormat targetFormat: Int

): ByteArray?

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Parameter Description:

• Data: source image data

• Width: the width of the image

• Height: The height of the image

• DataFormat: source ImageFormat, supported image formats, see the ImageFormat enumeration class

• TargetFormat: ImageFormat to be converted. For supported image formats, see the ImageFormat enumeration class

• Return value: Returns the converted data

  For example, a 640 * 480 resolution NV21 format data, now need to convert it to RGB24 format, we can call:

YuvUtils.imageFormatConvert(data.640.480.1.4)

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2.3 Images of various formats are converted into Bitmap

external fun imageToBitmap(

    data: ByteArray.

    width: Int.

    height: Int.

    @SupportFormat dataFormat: Int.

    bitmapConfig: Int

):Bitmap?

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Parameter Description:

• data: Source image data
• width: Width of the image
• height: Height of the image
• dataFormatFor details about the supported image formats, see source image formatImageFormatEnumeration class
• bitmapConfig: Bitmap format to be converted. Currently, only Bitmap format is supportedRGB565 和 ARGB_8888Two formatsBitmap
• The return value: Returns the convertedBitmap

2.4 Rotation and cropping operations for images of various formats

external fun dataClipRotate(

    data: ByteArray.

    @SupportFormat dataFormat: Int.

    width: Int.

    height: Int.

    @RotateDegree degree: Int.

    rect: Rect? .

    targetFormat: Int.

    priorityClip: Boolean

): ByteArray?

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Parameter Description:

• data: Source image data
• dataFormatFor details about the supported image formats, see source image formatImageFormatEnumeration class
• width: Width of the image
• height: Height of the image
• degree: Image rotation Angle, supported only0,90,180,270Four angles
• rect: Clipped rectangle coordinates, which can benullIs displayed, indicating that no clipping operation is performed
• targetFormat: Target image format to be converted. For details about supported image formats, seeImageFormatEnumeration class
• priorityClip: Whether to perform the cutting operation preferentially, cutting and then rotating and rotating and then trimming are two different operations
• The return value: Returns the converted data

Such as:

YuvUtils.dataClipRotate(

            rgba_data, 5, width, height, 90.

            Rect(100.0.300.300), 5.false

        )

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As you can see from the above operation, the selection of priorityClip is very important!

2.5 Images of various formats are transformed into relevant bitmaps through rotation and cropping

external fun dataClipRotateToBitmap(

    data: ByteArray.

    @SupportFormat dataFormat: Int.

    width: Int.

    height: Int.

    @RotateDegree degree: Int.

    rect: Rect? .

    bitmapConfig: Int.

    priorityClip: Boolean

): Bitmap?

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Parameter Description:

• data: Source image data
• dataFormatFor details about the supported image formats, see source image formatImageFormatEnumeration class
• width: Width of the image
• height: Height of the image
• degree: Image rotation Angle, supported only0,90,180,270Four angles
• rect: Clipped rectangle coordinates, which can benullIs displayed, indicating that no clipping operation is performed
• bitmapConfig: Needs to be converted toBitmapFormat, currently supported onlyRGB565 和 ARGB_8888Two formatsBitmap
• priorityClip: Whether to perform the cutting operation preferentially, cutting and then rotating and rotating and then trimming are two different operations
• The return value: Returns the convertedBitmap

2.6 Mirror flipping operation of images of various formats

external fun dataMirror(

    data: ByteArray.

    width: Int.

    height: Int.

    @SupportFormat dataFormat: Int.

    @SupportFormat targetFormat: Int.

    isVerticalMirror: Boolean = false

): ByteArray?

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Parameter Description:

• data: Source image data
• width: Width of the image
• height: Height of the image
• dataFormatFor details about the supported image formats, see source image formatImageFormatEnumeration class
• targetFormat: Image format to be converted. For details about supported image formats, seeImageFormatEnumeration class
• isVerticalMirror: Indicates whether to perform vertical mirroring. Default valuefalse, that is, flip horizontally, if istrueThat is, the image is carried out180Rotation, not true vertical mirror image
• The return value: Returns the converted data

For isVerticalMirror differences, see the following figure:

2.7 Zoom operation of images in various formats

external fun dataScale(

    data: ByteArray.

    width: Int.

    height: Int.

    dstWidth: Int.

    dstHeight: Int.

    @SupportFormat dataFormat: Int.

    @SupportFormat targetFormat: Int.

    @SupportFilter filterMode: Int = 0

): ByteArray?

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Parameter Description:

• data: Source image data
• width: Width of the image
• height: Height of the image
• dstWidth: Width of the target image
• dstHeight: Height of the target image
• dataFormatFor details about the supported image formats, see source image formatImageFormatEnumeration class
• targetFormat: Image format to be converted. For details about supported image formats, seeImageFormatEnumeration class

ImageUtils

The ImageUtils class is a secondary wrapper of the YuvUtils class, operating in each image format for easier external calls.

NV21 format image operation

The operation methods of NV21 image are as follows:

I420 format image operation

The operation methods of I420 format images are as follows:

The RGB24, RGB_565, and ARGB_8888 formats are similar to the interface methods shown above. In addition, some existing interfaces are the packaging of YuvUtils interface, and the basic operations are similar, not explained.