i am developing a iphone app. i have a background image lets say an airplane with black color out lines and from color palette user can pick a color and fill the region of airplane....any help, code , suggestion will highly be appriciated
A simple fill algorithm should do. just expand from the point you are on until you meet region end pixels
see http://en.wikipedia.org/wiki/Flood_fill you can also try googling for Boundary Fill algorithm
My first though was to have a UIView and a mask image on top of that with the plane but this only works in certain situations. If the shape of the plane does not change you could also change the color and then "fill" the plan in during the drawRect using functions like CGContextAddArc and CGContextAddRect.
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I want to put an outline around images but on some of the images the outline is broken. Notice the corners in the attached image.
I'm using 5 as the X and Y on the outline. In addition if I use a color besides black, the outline seems to be trying to blend. For example if I set the color to EEC209FF. See 2nd image.
So, i'm trying to explain both of your questions:
Why is the outline shape broken?
That’s the way the default Unity Outline script works: It just draws your UI.Image 4 time with the defined offset behind your image, it 4 different directions, which is cheap performance trick that fits most needs, but obviously not yours.
You can take a look at the Outline script on bitbucket here.
Why is the outline color partially yellow?
Unitys Outline Script draws your image in the background and multiplies the color values with your custom color.
That’s why the white part of your image on the upper right edge become yellow in the outline (almost the color you definied EEC209FF).
The outline on the lower right stays greens since it the take the colors from your image edge, approximately 19B754 multiplied with EEC209 to 178B03, which is a slightly dark green.
I want to fill the color in white area for Paint based application so please give me suggestion for how to do this work.
GPUImage is what you need there is a bunch of filters. In principle you need to point ios that it needs to change all whitecolors RGB(255.0,255.0,255.0) to some other color.
I'm looking for an algorithm to overlay a color on top of existing picture. Something similar to the following app (wall painter): http://itunes.apple.com/us/app/wall-painter/id396799182?mt=8
I want a similar functionality so I can paint walls in an existing picture and change them to a different color.
I can work both in yuv or rgb mode.
To successfully paint the walls in a picture, you have to do two steps:
Find the boundary of the wall within the picture (select the part of the image to be colored)
Apply the desired color to the selected area
The first step is the hard part. It similar to what Photoshop's magic wand tool would do. And indeed a search for magic wand algorithm turns up a few good articles such as this article with Objective-C code.
The second step is much easier and can be achieve with CGContextSetBlendMode and CGContextDrawImage.
You could try drawing into a graphics context with kCGBlendModeColor. From the documentation:
Uses the luminance values of the background with the hue and saturation values of the source image. This mode preserves the gray levels in the image. You can use this mode to color monochrome images or to tint color images.
Experimenting with other blend modes might also do the trick. See the documentation for details (search for "kCGBlendMode").
The RGB and YUV color models are not really great for changing colors in this way. I think the best color model for this is HLS.
Link: RGB to HLS and HLS to RGB conversion source code
H (hue) will change the base color
L (luminance) will change the brightness
S (saturation) will change the amount of color
You can evaluate the effect of these three components in a photo editing app, like Photoshop of The GIMP.
I have a scene with a background image (a lit room), and a black image (shadow) over that. I need to be able to move my finger over the background and reveal some parts of the scene, simulating a dim light source in a dark room.
My current approach was to generate a mask depending on the position of the touch, and then applying that mask to the shadow image. The problem is I'm generating a new mask and applying it every time I receive a touch event. It's a large image (800x600) and this causes the performance to go down and it increases a lot the memory usage, eventually crashing the game (I think I don't have any memory leaks, but that's not warrantied... anyway the performance itself isn't acceptable).
Can anyone think of a better approach (which doesn't involve using OpenGL ES -- that's not an option in this project) to do this?
To go with my comments above.
Maybe to get around the different shadow levels you could also have a grid of views (squares) between the image and the shadow view. each grid square has a different alpha opacity and when the spot is over a grid square, the grid square's alpha opacity changes to 0. when the spot moves off the grid square it's alpha opacity changes back to it's default.
Without more information it is a little difficult to know whether this approach will work in your case but what you could do is generate a single mask image, say, a radial alpha gradient and then apply an affine transform to it to shape it according to the touches. This can be used to simulate a torch/flashlight beam.
I would try this: use one view with a custom drawRect implemetation: first draw the shadow image (in grayscale) then a bright spot image in white an alpha. And finally the background image in a 'multiply' blend mode.
Just a thought, does the shadow has to be an image? Perhaps you could simply fill the shadow layer with a color and mask it then? This way the memory usage should be less and the effect should be nearly identical (if not exactly the same).
There is no reason to generate a new mask on every touch move. Instead, let the mask be initialized once and manipulate it (reset it's frame) as needed upon touch events.
I have a grayscale icon that I'm editing with Photoshop with a transparent background, but I can't, for the life of me, figure out how to convert the icon to one that can be used as an iPhone toolbar icon. If I simply save the image as a PNG, it doesn't show up as anti-aliased on the iPhone because every pixel with color is being rendered as black, instead of a shade of gray.
According to the Apple docs and other sources, there needs to be an alpha channel on the image to specify varying levels of transparency for each pixel. However, I have no idea what that means. I've read these posts and docs from Adobe and I still can't figure out how to properly convert a grayscale image into one that can be used as an iPhone toolbar icon. The blog post is hard to comprehend and poorly written, and the Adobe docs don't really help.
http://cahit.hayalet.net/blog/514/converting-an-image-to-iphone-toolbar-icon/
http://livedocs.adobe.com/en_US/Photoshop/10.0/help.html?content=WS74B356C9-353F-4483-8632-7B1A102F2A2E.html
Can someone point me in the right direction or provide exact, step-by-step directions to doing this in Photoshop?
It's much more simple than having to muck with actual masks in Photoshop.
iPhone toolbar icons are about 30px by 30px, so make a new Photoshop file with those dimensions. Ensure the background is transparent (you can specify that when creating a new file).
Then, any pixels you draw on top of this transparency become what iOS uses for the icon. Doesn't matter what color it is in Photoshop for NSToolbar icons -- they're automatically used as masks by iOS.
Leave transparent the parts you want to show through. Save as 24-bit PNG, and chuck into XCode as usual.
For a few icons that serve as good starting examples, check out the ones I publish for free here: http://glyphish.com Just take one of the PNGs and open it in Photoshop and you'll see that it's drawn in an arbitrary color (#444444) with varying levels of opacity to create darker and lighter parts of the icon.
This is more of a photoshop question than coding but anyway, here's a suggestion.
Lunacore has a good tutorial on how to use masks.
What you want to do is:
Make sure you're background is transparent.
Create a new layer and
fill it with any solid color.
Create a mask on the solid color
layer, and fill your greyscale image into the mask. (Use your
greyscale image as the mask.)
Toolbar icons use your image as a mask. They only consider what transparancy the image has. Not what color or shade.