I want to replace the particular color of an image with other user selected color. While replacing color of image, I want to maintain the gradient effect of that original color. for example see the attached images.
I have tried to do so with CoreGraphics & I got success to replace color. But the replacing color do not maintain the gradient effect of the original color in the image.
Can someone help me on this? Is the CoreGraphics is right way to do this?
Thanks in advance.
After some struggling almost with the same problem (but with NSImage), made a category for replacing colors in NSImage which uses ColorCube CIFilter.
https://github.com/braginets/NSImage-replace-color
inspired by this code for UIImage (also uses CIColorCube):
https://github.com/vhbit/ColorCubeSample
I do a lot of color transfer/blend/replacement/swapping between images in my projects and have found the following publications very useful, both by Erik Reinhard:
Color Transfer Between Images
Real-Time Color Blending of Rendered and Captured Video
Unfortunately I can't post any source code (or images) right now because the results are being submitted to an upcoming conference, but I have implemented variations of the above algorithms with very pleasing results. I'm sure with some tweaks (and a bit of patience) you might be able to get what you're after!
EDIT:
Furthermore, the real challenge will lie in separating the different picture elements (e.g. isolating the wall). This is not unlike Photoshop's magic wand tool which obviously requires a lot of processing power and complex algorithms (and is still not perfect).
Related
in an iOS application I need to recognize colors through camera, but analyzing the problem, I noticed that different kinds of light make the colors observed in the captured picture a little bit different from the real ones. For example, under a high neon light a light blue seems like a gray.
What is the cause and what kind of approch I could follow to solve this problem of "fake colors"?
The colors are not fake, they are just different than what you expect them to be. As #Piglet said this has a lot to do with the physics of light and white balance may help.
If you want to read more about it look at:
Color Rendering Index
Color Metamerism
Sensitivity Metamerism Index
Color Constancy
These all refer to the physics behind why different illuminations create different colors. There is also the camera color pipeline that contributes its share, so you can also read about white balance and tone mapping...
Let's say I have an image with a few colors.
I would like to replace programmatically a specific existing color by a new one.
(something simple, no need to support gradients, like I saw elsewhere).
E.g. I have an image showing a green circle and I want to display it as a red circle (every pixel initially defined with a given (R,G,B) is now displayed with a new (R,G,B).
Any idea of how to do that with the Apple ios SDK ? (or open source ...)
And btw what would be the best image file format to make this easier (png, jpg ....) ?
Thanks !
You should be able to do this using Core Image filters. the Color Cube CI filter lets you map a source color range to destination colors. You should be able to define a source color range and map it to different colors.
That's one CI Filter I didn't figure out how to use however. If you do a search on "Color Cube" in the Xcode help system there is sample code that does a "chromakey" effect that knocks out green shades to transparent. You should be able to adapt that to your needs.
I have a project on Github called CIFilterTest that shows how to use Core Image filters to process images. It's written as a general-purpose system that lets you try a wide variety of filters that use a standard set of parameters (points, colors, 1 or 2 source images, and floating-point values.) I never did take the time to generate the 3D color mapping "cube" that the color cube filter needs as input, so it doesn't allow you to use that particular filter. You'll have to look at the color Cube sample code in the Xcode docs to generate inputs for the Color Cube filter, but my sample app should help a great deal with the basic setup for doing CI based image processing.
answered similar question here:
Replace particular color of image in iOS
in short: I would suggest using CoreImage filter.
The grid is a blue/green. The work is in a black ink, and has a fair bit of variety of pressures, which I want to retain.
Here's a link to a small selection.
I have Photoshop v3
My attempts have involved using Select, Color Range, and sampling some grid, then inverting.
Is there a better way?
I also have some experience with Python and PIL, if that's a useful alternative.
This is a Photoshop answer, rather than a programming answer, but that seems to match your question's needs.
I applied a Black and White filter, and enabled a Blue filter, then set the Blue channel sensitivity to 300%, like this in Photoshop CC.
and got pretty good results like this:
In an older vsersion of Photoshop, you may need to go to Image->Mode->Lab Color and then go into the Channels palette and deselect Lab leaving just a and b channels selected, then use Select->Color Range to get the blues (or maybe the blacks!!!!) before going back to RGB mode.
I am in my final year of BS Computer Science. I have chosen a project in the image processing domain. But I really don't know where to start from! Here is a rough draft of my project idea:
Project Description:
Often people are faced with the problem of deciding which colors to choose to paint their walls, doors and ceilings. They want to know how their rooms will look like after applying a certain color. We want to design a mobile application that can give people the opportunity to preview their rooms/walls/ceilings, etc, with a certain color before applying the color. Through our application the user can take photos of their rooms/walls/ceilings, etc, and change their colors virtually and preview them. This will give them a good estimate about the final look of their house.
Development will be in java using open CV libraries.
Can anyone provide some help?
For starting OpenCV with android you can follow the tutorial here.
And as your above description, I think you need to do the following...
Filter out the color of room's wall or ceiling color.
Replace with your preview color.
But as your room's color is not unique, you may need to mark the color manually and segment it. Here watershed algorithm might be helpful.
And one more thing is that there might be a chance of lighting variation, so you should use HSV color space instead of RGB.
And finally this is not the full solution, but you will get some idea about how to start with your project.
ImageMagick as a famous image processing library.You may look that one too.It can perform numerous operations with images
Thanks
I need to develop a software that selects a face from a photo where the background is a plain color (green, like in the movies).
Then we want to compose that selection with another background image, this part is easy with many libraries. But I don't know how can I do the selection? Can you give some links or libraries to investigate? I can do this project with any language of my choose, so examples or links in any language are welcome.
Ok, what you are trying to do is called chroma key. Like you say, it used a lot in the movies with a blue/green screen. On windows its actually pretty easy to do because its built into windows as part of GDI+ (or on C#, I think its just called the Graphics class).
I dont have any sample code handy, but the process is pretty straight forward:
With GDI+, you create a bitmap object of your foreground image (the one with the green background). Then create an ImageAttributes object. Use ImageAttribute's object's SetColorKey() method to specify a color or range of colors to use as the background color. Lastly, draw that bitmap object over the target bitmap, and GDI+ will draw it as if the background color is transparent.
There's more to it in that in code, but concept-wise thats all there is to it.
This is probably an area where it is easier to work in some other space than RGB - such as HSV.
I would also look at the OpenCV library.