using QGIS, I have constructed a colour map that looks similar to the one below.
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I would like to obtain a similar triangular legend, but with the colours used in my RGB composite and based on the blending mode I used. I know how to construct bar colour ramps, but I struggle fitting the colour space present in my RGB composite to the desired layout, where each corner stands for a given colour channel. I have extensively searched the internet, but so far have found little. Can such task even be accomplished in QGIS? If it is possible, I appreciate every help!
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I need to set up a clickable image system for dynamically created content. The image consists of a background image, and several grey-scale mask images.
Background Image:
(source: goehler.dk)
Masks:
(source: goehler.dk)
,
(source: goehler.dk)
,
(source: goehler.dk)
,
(source: goehler.dk)
,
(source: goehler.dk)
Each area, defined by a mask, should be highlighted on mouse over, clickable on the image, and open a certain link.
How do I do this the smartest way? I need this to be responsive, and work with a couple of hundred masks.
I haven't tried anything yet, but I've done some research, which have resulted in two possible solutions:
A. Trace the masks, and create imagemap coordinates for each, which can be overlayed the original image. (seems difficult, especially with masks that have holes).
B. Layer all masks on top, and shuffle through them and search for white pixels. (seems processor intensive, shuffling though hundres of images).
I hope however, that there is a third, simpler, more optimized and more elegant solution?
Any advice?
I'd love to hear from anyone who have any experience with something similar.
You should try to precompute as much of this as possible, especially because it's probably not feasible to download hundreds of these mask images in the user's browser.
Your solution A seems like a good way to go, provided it's possible to compute coordinates from the pixel shapes.
Another idea could be combining the mask images in a single image by color-coding the mask shapes (filling each shape with a different color). Colors can be assigned randomly as long as they are used only once. Along with that, provide a simple lookup table for the color-to-shape mapping (e.g. #f00 => cube, #0f0 => donut, ...). Now, when the original image is clicked:
Find the pixel coordinate of the click
Lookup the color in the mask image at the same coordinate
Lookup the shape for the color in the lookup table
First of all, even with 100s of masks, this should not be slow, because the required algorithm has a complexity of O(n) and that is not slow.
The only bottleneck you will have is the pixel lookup, which is an expensive operation (unless you do certain modifications).
I would go with B.
Lets say your mouse coordinates are x:400, y:300, relative to your background image which has the dimensions 800x600.
You would iterate over all masks, and check:
mask.getPixel(400, 300) == white?
If so, use that mask, blend it over the original image with a specific alpha factor so the background get grayed out.
The bottleneck is: mask.getPixel()
You would have to do that n times if you have n masks and its the last one.
As I stated, its an expensive lookup; so can you optimise it?
Yes, cut out unnecessary look-ups by using: bounding boxes.
But to use bounding boxes, you must first create the bounding box data for each mask, which you could do once when you load (no problem).
The bounding box defines the upper left and bottom right corner that "bounds" the white area snugly. In other words, you must determine min and max X & Y coordinate where the pixel is white.
If the mouse coordinates are outside of this box, do not bother making a lookup, as it will certainly not be in the white area.
Edit: Since I was bored, I went ahead and implemented it...
Check it out.
//preProcessMasks() & trackMouse() is where everything happens
Gotto have the background image "img.jpg" and the masks "1.jpg" .. "5.jpg" in the same folder!
Works with firefox, chrome says "The canvas has been tainted by cross-origin data"... its a quick n dirty hack, do whatever you want with it, if its of any use to you!
I’ve working in an app system that take the ID Photos, but the webcam whitebalance ajust isn’t perfect.
In the background we put an white fabric but it still look other color (kind of yellow, gray, blue, depending of the light at the moment of the snapshot).
I’m trying to work with the blend mode “hardlight” in the webcam, plus magicWand to remove the background and turn it completely white, but the skin tone doen’t look natural.
Using the levels correction in photoshop, I can define the right point of White and then use the MagicWand to clean the image.
How can I do the same using AS3?
I would look into using the paletteMap functionality built into bitmapData. It allows you to replace colour values on a per colour index basis.
You could, in theory, use a picker to choose the White balance point, and then use that as an offset for the palletteMap values.
Read more about palletteMap here:
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/display/BitmapData.html#paletteMap()
I'm having trouble understand how DisplacementMapFilter works. Basically, I'm trying to create a revolving planet through a combination of fisheye/masking.
Also, how do I go about doing this via timeline? I'm not too familiar with coding within it, but this is more of an animation project than anything else, so classes are out of the question. Sorry for the lack of code -- I'm simply stuck.
As noted in the comments above, this probably only answers half the problem;
Generating a displacement map image isn't too difficult with the right tools. I'll assume you're using Photoshop, GIMP, Fireworks, or similar.
It's probably best to work on a 128x128 image or smaller with this method. Some editors have more specialised tools which let you work on pretty much any size of image, but this is a generic process that needs no special tools. You can always enlarge the end result, but the quality will begin to go down.
Start with a gradient fill. It should go from pure black on the left to dark red on the right (specifically 128,0,0). Add a vertical fill from black at the top to dark green at the bottom (specifically 0,128,0), and combine them with a LIGHTEN or ADD filter. You should now have an image which has black, red, green and yellow corners. Flatten it.
Copy this image to another layer / whatever the term-of-choice is for your editor. Apply whatever displacement filter you want to it (maybe a fish eye, maybe a manual smudge, maybe a perspective transform, anything)
Add a third layer between the two. Flood-fill it with dark yellow (128,128,0) and set it to ADD / ADDITION blend mode. Set the top layer to SUBTRACT / SUBTRACTION blend mode.
That's it. You should get a mostly yellow image which will function as a displacement map.
Update:
To use this in the example program (http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/filters/DisplacementMapFilter.html#includeExamplesSummary), replace the createBitmapData function with this:
private function createBitmapData():BitmapData {
return myBitmapObject.bitmapData;
}
where myBitmapObject is the instance name (I think) of your displacement Bitmap. There are tidier ways of setting that up, but this is the easiest.
Given an HTML canvas that has already been drawn to, what's the best way to shade the whole canvas except given circular regions? (in context: shadows except where are there light sources)
I was hoping it would be as simple as a rect() followed by subsequent arc()s, but AFAIK there's no way to "remove" those circular sections after the fact. I can get close ( http://jsfiddle.net/mW8D3/2/), but the overlapping regions of circles end up shaded (in XOR fashion, whereas I want OR). Using clip() has the same problem.
I've also tried using globalCompositeOperation but can't quite seem to achieve what I want.
Any ideas?
You could first create the shadow image on a second canvas and knock out holes from it with globalCompositeOperation 'copy' and a transparent fillStyle.
Like this: http://jsfiddle.net/mW8D3/4/
I'm using KImageMapEditor on Linux (Ubuntu) to create an image map. The shapes in the image are a little complex so I'm using the freehand tool to draw them. However, this is really the same as the polygon tool so the shapes have ended up with a lot of points, which has made the HTML pretty huge.
Does anyone know of a way to reduce the complexity of the shapes, like "smoothing out" the lines?
I should also mention the reason I want the shapes to be fairly accurate is because I'm intending to do something like this, where each shape is highlighted on mouseover: http://davidlynch.org/js/maphilight/docs/demo_usa.html
Since users aren't going to click to the pixel, give them some leeway and create a "sloppy" map which roughly outlines each shape instead of clinging to the actual pixel outline.
This is in the same way as you don't expect a click on a link to fail just because you click on the background which shines through the text. You expect the bounding box of the text to act as the click-able area instead of the "black pixels".
Algorithm: Given three consecutive points, eliminate the middle point if the angle created is less than some tolerated error e.
Polygonal path simplification with angle constraint