I would ,like to be able to modify image RBG values based on combination of: a) neighbouring RBG values; b) user parameter inputs. I light to experiment with various colour abstractions of my images. I have not found any expressions in help material, or corresponding forum answers. Is this something already available? If so, where? Otherwsie could this capability be added to the equations/expressions capability of Affinity Photo.
The equations facility in Affinity is not well documented. There is limited support in some AP actions, but the Transform and Distort > Equations filter offers a wide range of functions. This tutorial focuses on using the trigonometrical functions, sine, tangent and arctangent. The argument to many trigonometrical functions is an angle. In mathematics this is usually expressed in radians. However, the Affinity functions expect their argument in degrees. Sines and cosines The argument expected is in degrees, and over 360 degrees, the value of the function varies between -1 and +1. The sine function starts at zero and rises to a maximum at 90 deg, then falls to zero at 180 deg, falling to a minimum of -1 at 270 deg before rising to zero at 360 deg. If we wish to map this cycle to the width of an image, then we can use sin(360*x/w). Typically we would want the amplitude of the cycle (the maximum and minimum) to be more than 1 and -1, so we add a scale factor, measured in pixels. For an amplitude of 100 pixels, we have 100*sin(360*x/w). This gives one cycle across the width of the image. If we want more than one cycle, we can add a multiplier in the argument, so for three cycles per width, we can use 100*sin(3*360*x/w). Note that I use 3*360 rather than 1080 since it preserves the standard 360 multiplier. As an example, here is a checkerboard with Filter > Distort > Equations: x=x y=y+100*sin(2*360*x/w) If we apply this to a real image, we get: This is varying the vertical position of a point along the x-axis. We could vary the vertical position of a point along the y-axis by using the equation: y=y+100*sin(2*360*y/h) For the checkerboard, this would give: And for the Severn Bridge we get: We could even combine them both with the formula: y=y+100*sin(2*360*x/w)*sin(2*360*y/h) to give: or, for a real image: I will be adding further examples using tangents and cotangents.
Equations - a general comprehensive overview?
I have been trying to devise a macro using the Distort > Equations, but it is hampered by a lack of documentation. I recall having once seen a list of supported functions, but I cannot now locate it. Neither Affinity help, this forum nor even Google have revealed this. I assume the same engine will apply to Transform using Equations. Can anyone please tell me where it could be found?
When using Apply Image equations, I am expecting to see a completely greyscale image when Da and Db are set to constant 0 in LAB space, however I see a heavy blue tint. See attached screenshot, left side should be greyscale instead.
First post here. I've been working on a composite of images captured during totality & getting some banding artifacts in PS when forced to use 16 bit mode rather than 32 bit for sharpening steps. I'd like to make sure Affinity Photos has the adjustments I need in 32 bit mode. The complete workflow for PS is describe in this tutorial by Russell Brown: PS Spin Blur Eclipse Processing From Photos tutorials, I see there are spin-blur filters, Apply Image: Equations panel & an Equations panel. So maybe everything I node is there but done differently in Photos. The key step I'm unsure about is in one of the equations panels. In PS, a duplicate image is spin blurred & the alpha channel of that image is subtracted from the original alpha w/ an off-set of 128 in the Calculations panel to give a low contrast mid-gray frequency mask. That mask is then Overlayed onto the original. I'd like to confirm that all this can be done in Photos in 32 bit mode? Here is a version of my PS work from 77 images w/ artifacts & a mask. The frequency mask reveals the finer corona detail. Thanks!
Does someone know how to implement Floyd-Steinberg or Jarvis, Judice, Ninke dithering with equations? Is that even possible at this point?
Trying out the awesome new Equations feature in "Apply Image", I found that expressions that lead to out-of-bounds values are not handled gracefully (8-bit mode). My test was a simple color difference greenscreen keyer: DA = SG - max(SR, SB) The result has artifacts where this expression yields negative results. Doing the clamping manually works fine. DA = max(0, SG-max(SR, SB)) It would make more sense to always have this clamping performed automatically and implicitly for non-float documents. This would also ensure that more expressions and macros created for unbounded floating point images will work with 8-bit and 16-bit documents without adjustments. I have also not been able to find out how to access the current pixel's coordinates inside Apply Image (seems to work for "Distort > Equations" expressions) and what the syntax for modulo operators is, but that's likely either due to my stupidity or it not being implemented yet and not a bug. Also, I noticed a strange 1-pixel diagonal line pattern when choosing a source layer and then navigating to an adjustment layer in the Layers panel.