sub_image — Subtract two images.
The operator sub_image subtracts two images. The gray values (g1,g2) of the input images (ImageMinuend and ImageSubtrahend) are transformed as follows:
g' := (g1 - g2) * Mult + AddIf an overflow or an underflow occurs the values are clipped. Note that this is not the case with cyclic and direction images.
Several images can be processed in one call. In this case both input parameters contain the same number of images which are then processed in pairs. An output image is generated for every pair.
Please note that the runtime of the operator varies with different control parameters. For frequently used combinations special optimizations are used. Additionally, for byte, int2, and uint2 images special optimizations are implemented that use SIMD technology. The actual application of these special optimizations is controlled by the system parameter 'mmx_enable' (see set_system). If 'mmx_enable' is set to 'true' (and the SIMD instruction set is available), the internal calculations are performed using SIMD technology.
sub_image can be executed on an OpenCL device for byte, int1, int2, uint2, int4, real, direction, cyclic, and complex images. However, since for OpenCL 1.0 only single precision floating point is supported for all devices, and not all rounding modes are supported, the OpenCL implementation can produce slightly different results from the scalar or SIMD implementations.
Note that the acceleration gained by SIMD technology is highest on large, compact input regions. However, in rare cases, the execution of sub_image might take significantly longer with SIMD technology than without, depending on the input region and the capabilities of the hardware. In these cases, the use of SIMD technology can be avoided by set_system(::'mmx_enable','false':).
Result image(s) by the subtraction.
Default value: 1.0
Suggested values: 0.0, 1.0, 2.0, 3.0, 4.0
Typical range of values: -255.0 ≤ Mult ≤ 255.0
Minimum increment: 0.001
Recommended increment: 0.1
Default value: 128.0
Suggested values: 0.0, 128.0, 256.0
Typical range of values: -512.0 ≤ Add ≤ 512.0
Minimum increment: 0.01
Recommended increment: 1.0
read_image(Image1,'fabrik') dev_display (Image1) read_image(Image2,'monkey') dev_display (Image2) sub_image (Image1, Image2, Result, 1, 100) dev_display (Result)
The operator sub_image returns the value 2 (H_MSG_TRUE) if the parameters are correct. The behavior in case of empty input (no input images available) is set via the operator set_system(::'no_object_result',<Result>:) If necessary an exception is raised.
add_image, mult_image, dyn_threshold, check_difference