Operator Reference
linear_trans_color (Operator)
linear_trans_color — Compute an affine transformation of the color values of a
multichannel image.
Signature
linear_trans_color(Image : ImageTrans : TransMat : )
Description
linear_trans_color performs an affine transformation of the
color values of the multichannel image Image and returns
the result in ImageTrans. The affine transformation of the
color values is described by the transformation matrix
TransMat. If n is the number of channels in
Image and m is the number of channels in
ImageTrans, TransMat is a homogeneous m × (n+1) matrix that is stored row by row. Homogeneous
means that the left m × n submatrix of
TransMat describes a linear transformation of the color
values, while the last column of TransMat describes a
constant offset of the color values. The transformation matrix is
typically computed with gen_principal_comp_trans. In
particular, it is possible to project an image onto the first m
principal components by selecting the first m ×
(n+1) values of the transformation returned by
gen_principal_comp_trans. The transformation can, however,
also be specified directly. For example, a transformation from RGB
to YIQ, which is described by the following transformation
can be achieved by setting TransMat to
[0.299,0.587,0.114,0.0,0.599,-0.276,-0.324,127.5,0.214,-0.522,0.309,127.5]
Here, it should be noted that the above transformation is
unnormalized, i.e., the resulting color values can lie outside the
range [0,255]. The transformation 'yiq' in
trans_from_rgb additionally scales the rows of the matrix
(except for the constant offset) appropriately.
To avoid a loss of information, linear_trans_color returns
an image of type real. If a different image type is desired, the
image can be transformed with convert_image_type.
Attention
linear_trans_color can be executed on OpenCL devices if the image
Image consists of nine channels or less and is transformed to
an image of three channels or less. Since the calculations are done in
single precision floating point, the results may differ from those
calculated by the CPU.
Execution Information
- Supports OpenCL compute devices.
- Multithreading type: reentrant (runs in parallel with non-exclusive operators).
- Multithreading scope: global (may be called from any thread).
- Automatically parallelized on tuple level.
- Automatically parallelized on domain level.
Parameters
Image (input_object) multichannel-image(-array) → object (byte / direction / cyclic / int1 / int2 / uint2 / int4 / real)
Multichannel input image.
ImageTrans (output_object) multichannel-image(-array) → object (real)
Multichannel output image.
TransMat (input_control) real-array → (real)
Transformation matrix for the color values.
Result
The operator linear_trans_color returns the value 2 (
H_MSG_TRUE)
if
the parameters are correct. Otherwise an exception is raised.
Possible Predecessors
Possible Successors
Alternatives
principal_comp,
trans_from_rgb,
trans_to_rgb
Module
Foundation