Function

vImageConvert_ARGB8888toRGB565(_:_:_:)

Converts an ARGB8888 image into an RGB565 image.

Declaration

func vImageConvert_ARGB8888toRGB565(_ src: UnsafePointer<vImage_Buffer>, _ dest: UnsafePointer<vImage_Buffer>, _ flags: vImage_Flags) -> vImage_Error

Parameters

src

A pointer to a vImage buffer structure that contains the source image whose data you want to convert.

dest

A pointer to a vImage buffer data structure. You're responsible for filling out the height, width, and rowBytes fields of this structure, and for allocating a data buffer of the appropriate size. On return, the data buffer this structure points to contains the destination image data. When you no longer need the data buffer, you must deallocate the memory.

flags

The options to use when performing the operation. If you plan to perform your own tiling or use multithreading, pass kvImageDoNotTile.

Return Value

kvImageNoError; otherwise, one of the error codes described in Data Types and Constants.

Discussion

The alpha channel in the ARGB8888 image is ignored. (The RGB565 format has 16-bit pixels with 5 bits for red, 6 for green, and 5 for blue.) The function calculates the pixels in the destination image as follows:

    uint32_t red   = (8bitRedChannel   * (31*2) + 255) / (255*2)
    uint32_t green = (8bitGreenChannel * 63 + 127) / 255
    uint32_t blue  = (8bitBlueChannel  * 31 + 127) / 255
    uint16_t RGB565pixel = (red << 11) | (green <<  5) | blue

See Also

Converting from ARGB Formats

func vImageConvert_ARGBFFFFtoRGBFFF(UnsafePointer<vImage_Buffer>!, UnsafePointer<vImage_Buffer>!, vImage_Flags) -> vImage_Error

Converts a four-channel ARGBFFFF image to a three-channel RGBFFF image by removing the alpha channel.

func vImageConvert_ARGB8888toRGB888(UnsafePointer<vImage_Buffer>, UnsafePointer<vImage_Buffer>, vImage_Flags) -> vImage_Error

Converts a four-channel ARGB8888 image to a three-channel RGB888 image by removing the alpha channel..