vImageConvert_ARGB16UToARGB8888(_:_:_:_:_:_:)
Converts an unsigned 16-bit-per-channel, 4-channel interleaved buffer to an 8-bit-per-channel, 4-channel interleaved buffer.
Declaration
func vImageConvert_ARGB16UToARGB8888(_ src: UnsafePointer<vImage_Buffer>, _ dest: UnsafePointer<vImage_Buffer>, _ permuteMap: UnsafePointer<UInt8>, _ copyMask: UInt8, _ backgroundColor: UnsafePointer<UInt8>, _ flags: vImage_Flags) -> vImage_ErrorParameters
- src:
The source vImage buffer.
- dest:
A pointer to the destination vImage buffer 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, deallocate the memory to prevent memory leaks.
- permuteMap:
An array of four 8-bit integers with the values
0,1,2, and 3, in some order. Each value specifies the channel from the source image that the function copies to the destination channel at the corresponding index. - copyMask:
A bitmask that specifies the channel from the background color that the function copies to the destination channel at the corresponding index. The
1000bit corresponds to the alpha channel, the0100bit corresponds to the red channel, the0010corresponds to the green channel, and the0001bit corresponds to the green channel. - backgroundColor:
A 16-bit-per-channel, 4-channel pixel value that replaces the destination pixels based on the copy mask.
- flags:
The options to use when performing the operation. If your code implements its own tiling or its own multithreading, pass Kvimagedonottile; otherwise, pass Kvimagenoflags.
Return Value
kvImageNoError; otherwise, one of the error codes in Data Types and Constants.
Discussion
The function uses the following calculation to perform the conversion:
Pixel_16U *srcPixel;
Pixel_8888 *destPixel;
uint16_t result16;
uint8_t result[4];
uint8_t mask = 0x8;
for( int i = 0; i < 4; i++ )
{
result16 = srcPixel[ permuteMap[i] ];
result[i] = (result16 * 255U + 32767U) / 65535U;
if( mask & copyMask )
result[i] = backgroundColor[i];
mask = mask >> 1;
}
srcPixel += 4;
destPixel[0] = result[0];
destPixel[1] = result[1];
destPixel[2] = result[2];
destPixel[3] = result[3];
destPixel += 4;