At present I'm generating a chart based on a bunch of user-selected options, and this is rendered on the server to generate a png output file. The generated png chart is then displayed on the user's system, over an underlying system background.
Where the plotBackgroundColor of the chart has some opacity, the user's underlying system background will of course show through, and will influence how the chart appears.
That's all fine, because the user has complete control over both the highcharts plotBackgroundColor and the system background colour.
But now I want to generate a chart that is "free standing", with a solid background colour (no opacity) which represents exactly how the chart appears when over the system background. That way, I can display that chart on any system, to give a true picture of what the user is seeing, regardless of the system background colour in the target device.
I do have access to the user's system background colour (it's either a bitmap, or I can just extract the "dominant" colour somehow and use that as a solid colour instead if it's easier).
So using the concept of layers, this would be like merging the highcharts plotBackgroundColor with a solid colour that represents the system background colour, and using that as plotBackgroundColor instead.
Or maybe there's a way to change an underlying background "browser" colour that is used in the highcharts renderer, independent of plotBackgroundColor?
I'm sure this must be possible somehow?
One way of doing this, and it's what I'm doing until someone posts a better answer, is just to manually combine each backgroundColor value with the underlying system canvas colour, using the method described at https://stackoverflow.com/a/10782314/4070848. This is basically just laying one colour over the other, and using an algorithm to determine the combined colour based on the respective opacities and rgb values.
I check whether the backgroundColor is a plain colour or a linear/radial gradient, and if the latter then I combine each of the stop colours separately with the underlying colour and reconstruct the gradient based on the merged stop colours.
Seems to work OK, but maybe there's an off-the-shelf method, or maybe someone can tell me how to do it better...!
Related
Simple I have UIImageView icon with two people and it looks like this:
but when I set tintColor to red it looks like this:
Is there any way to avoid covering every non zero-alpha pixel? I need to show the tie really there. One time I need people red, other time green.
The icon is simple png file. Rounded circle is simple background color of UIImageView. So the part of the image with tie cannot be zero-alpha.
Is there any way to achieve such effect WITHOUT creating images for every color?
This was similar to another idea I had been playing around with, so I did a little more fiddling...
Starting with these 3 images:
and then using them as .withRenderingMode(.alwaysTemplate) to give the desired colors... and then layering them via CALayer to get:
and an "exploded" view for clarity...
Create an image where the "people" are 100% transparent - effectively "holes" in the image.
Set the background color of the UIImageView to be the "fill" color.
You can still mask it with a circle (CAShapeLayer, for example), if you don't want a white bounding-box as part of the image.
Original images:
https://i.stack.imgur.com/eFrmB.png
https://i.stack.imgur.com/2GNDX.png
Use the CISpotColor filter:
https://developer.apple.com/library/content/documentation/GraphicsImaging/Reference/CoreImageFilterReference/#//apple_ref/doc/filter/ci/CISpotColor
This allows you to specify a color in your image that is to be changed into another color. Thus, since you know the original color of the tie and the background, you can change either of them, or both, in a single move.
I have a python-fu script, which is mostly working. It scans a layer looking for a color, rectangular selects contiguous areas of that color, copies the portion of image in another layer covered by that selection, and saves it to a separate file. All good.
Now the rectangular select has to be cleared, so that it won't be selected again as part of some other set, and the scan starts over so that it can find the next contiguous rectangular block to save.
Unfortunately, I can see the scan traverse the area that's been cleared, and the debug output shows that it still thinks the color is there. Despite the fact that I can see the area is transparent. So, I must be missing a step that tells gimp to update.
I thought I had it with the following:
pdb.gimp_edit_clear(layer)
pdb.gimp_drawable_update(layer,0,0,width,height)
gimp_edit_clear does clear the selection in the layer I'm searching -- I see that happen -- but the gimp_drawable_update doesn't seem to do anything, because when the loop progresses over the spot that's been cleared, it reports that the old color is still there.
What am I missing?
The problem was not with the clear, but with my understanding of what it did. I thought it erased the area reverting it to the natural color of an originally transparent area which is RGBA(0,0,0,0). That's what GIMP reports when you ask for the color of a pixel in a fresh transparent layer.
'Clear' doesn't actually remove the color, it just sets the transparency to 100%. So if the original color had been "fully visible white" RGBA(1,1,1,1), it just turns it to "invisible white" RGBA(1,1,1,0).
I had misunderstood RGBA(0,0,0,0) as "transparent", when it's really "invisible black".
So, when my scan started again, it was still seeing 'white', albeit 'invisible white'. Now, instead of using 'clear', I do a fill with the background color, which I've deliberately set to "invisible black".
Basically I want to apply chroma key filter to ios live camera feed but I want user to pick the color which will be replaced by another color.
I found some examples using green screen but I don't know how to replace color dynamically instead of just green color.
Any idea how can I achieve that with best performance?
You've previously asked about my GPUImage framework, so I assume that you're familiar with it. Within that framework are two filters, a GPUImageChromaKeyFilter and a GPUImageChromaKeyBlendFilter. Both will key off of whatever color you specify via the -setColorToReplaceRed:green:blue: method, with a threshold set using the thresholdSensitivity property.
The former filter merely turns areas matching the color within the threshold to an alpha of 0, with the latter actually doing a blend against another image or video source based areas of the input image or video that match. The FilterShowcase example application shows how to do this for green, but you can set the keying color to anything you want.
Please be kind, I'm new to this....
I have an application that I'm developing where I need to take a PNG image, which has a transparency layer, and treat another color (I'm thinking of using RGB( 1, 1, 1 ), since it's so close to pure black that I can hard-code it) as a separate transparency layer. The reason for this is that I have a background image sitting behind the PNG image that I would like to still display as my sprite gets filled (by adding a progress bar to the sprite), and I only want the portions of the sprite that aren't of the given color to reflect the color fill of the progress bar. In this way, I can avoid having to deal with vector computations for the outline of the image within the sprite, flood the area outside of the discernable image with my new "transparent" color, and be on my merry way.
I've tried using shaders, but they seem to be less than helpful.
There is no way that I know of due to Open GL not allowing you to do it. You will either have to modify the pixel data manually or write a shader (Which you hav already done ).
I need to draw an interactive map for an iOs application. For example it can be the map of the US showing the states. It will need to show all the states in different colors ( I'll get this from a delegate colorForStateNo: ) It will need to allow the user to select a state by touching it, when the color will change, and a "stick out" effect should be shown, maybe even a symbol animated to appear over the selected state. Also the color of some states will need to change depending on external events. This color change will mean an animation like a circle starting in the middle of the state and progressing towards the edges changing the color from the current one to the one inside the circle.
Can this be done ,easily in core-graphics? Or is it only possible with Open GL ES? What is the easiest way to do this? I have worked with core graphics and it doesn't seem to handle animation very well, I just redraw the entire screen when something needed to move... Also how could I use an external image to draw the map? Setting up a lot of drawLineToPoint seems like , a lot of work to draw only one state let alone the whole map ...
You could create the map using vector graphics and then have that converted to OpenGL calls.
Displaying SVG in OpenGL without intermediate raster
EDIT: The link applies to C++, but you may be able to find a similar solution.