i have two images of exact size . Imagine two images of a room, one with sunlight and another with artificial light.I have to place them one over other and add a slider,so that when slider is moved the below image will show according to slider value. Ex - If slider is on half position then user will be able to show half of image with sunlight and half with artificial light giving it a curtain effect.
i have searched a lot and failed to find any clue as how to do this. Please suggest any tutorial to do this kind of animation.
Thanks
Set the sliders minimum value to 0 and it's maximum value to 1
[mySlider setMinimumValue:0.0f];
[mySlider setMaximumValue:1.0f];
When the slider is changed by the user get the current value
float sliderProgress = mySlider.value;
adjust the alpha values of both images dependant upon the value.
[imageSunlight setAlpha:sliderProgress];
and the other image's alpha would be
[imageArtificialLight setAlpha:(1.0f - sliderProgress)];
Related
I have sRGB images with color casts. To remove it manually I usually use Photoshop Level Adjustments. Photoshop also have tools for that: Auto Contrast or even better Auto Tone which also takes shadows, midtones & highlights into account.
If I remove the cast manually I adjust each of the RGB channels individually so that the darkest pixels are set to pure black and the lightest to pure white and then redistribute all other values (spreading the histogram). This is a simple approach but shows good results for my images.
In my node.js app I'm using sharp for image processing which uses libvips as its processing engine. I tried to remove the cast with .normalize() but this command works on all channels together and not individual for each of the RGB channels. So it doesn't work for me.
I also asked this question on the sharp project page. I tested the suggestion from lovell to try it with hist_local but the results are not useable for me.
Now I would like to find out how this could be done using the native libvips. I've played around with nip2 GUI and different commands but could not figure out how it could be achieved:
Histogram > Equalise Histogram > Global => Picture looks over saturated
Image > Levels > Scale to 0 - 255 => Channels ar not all spreading from 0 - 255 (I don't understand exactly what this command does?)
Thanks for every hint!
Addition
Here is a example with pictures from Photoshop to show what I want.
The source image is a picture of a frame from a film negative.
Image before processing
Step1 Invert image
Image after inversion
Step2 using Auto tone in Photoshop (works the same way as my description above about manually remove the color cast)
Image after Auto Tone
This last picture is ok for me.
nip2 has a menu item for this.
Load your image and mark a region on it containing the area you'd like to be neutral. It can be any lightness, it doesn't need to be white.
Use File / Open to get the file dialog and you should see the image loaded in your workspace as a thumbnail.
Doubleclick on the thumbnail to open an image view window.
In the view window, zoom and pan to the right spot. The user guide (press F1) has a section on image navigation.
Hold down CTRL and click and drag down and right to mark a rectangular region.
Back in the main window, click Toolkits / Tasks / Capture / White balance. You should see something like:
You can drag an resize your region to change the neutral point. Use the colour picker to set what white means. You can make other whites with (for example) Colour / New / Colour from CCT and link them together.
Click Colour / New / Colour from CCT to make a colour picker from CCT (correlated colour temperature) -- the temperature in Kelvin of that white.
Set it to something interesting, like 4800 for warm white.
Click on the formula for A5.white to edit it, and enter the cell of your CCT widget (A7 in this case).
Now you can drag the region to adjust the pixels to set the neutral from, and drag the CCT slider to set the temperature.
It can be annoying to find things in the toolkit menu. There's a thing for searching toolkits: in the main window, click View / Toolkit browser. You can enter something like "white" and it'll show related toolkit entries.
Here's another answer, but using pyvips and responding to the previous comments. I didn't want to delete the first answer as it still seemed useful.
This version finds the image histogram, searches for thresholds which will select 0.5% and 99.5% of pixels in each image band, then rescales the image so that those pixel values become 0 and 255.
import sys
import pyvips
# trim off this percentage of pixels from the top and bottom
trim_percent = 0.5
def percent(hist, percentage):
"""From a histogram, find the threshold above which lie
#percentage of pixels."""
# normalised cumulative histogram
norm = hist.hist_cum().hist_norm()
# column and row profile over percentage
c, r = (norm > norm.width * percentage / 100).profile()
return r.avg()
image = pyvips.Image.new_from_file(sys.argv[1])
# photographic negative
image = image.invert()
# find image histogram, split to set of separate bands
bands = image.hist_find().bandsplit()
# for each band, the low and high thresholds
low = [percent(band, trim_percent) for band in bands]
high = [percent(band, 100 - trim_percent) for band in bands]
# rescale image
scale = [255.0 / (h - l) for h, l in zip(high, low)]
image = (image - low) * scale
image.write_to_file(sys.argv[2])
It seems to give roughly similar results to the PS button. If I run:
$ ./autolevel.py ~/pics/before.jpg x.jpg
I see:
In the meantime I've found the Simplest Color Balance Algorithm which exactly describes the problem with color casts and there you can also find a C source code.
It is exactly the same solution as John describes in his second answer but as a small piece of c-code.
I'm now trying to use it as C/C++ addon with N-API under node.js.
I imagine there is probably going to be an easy solution for this in GIMP, but I for the life of me can't figure it out.
I'm using the color picker tool with the use info window selected to verify pixel values.
Basically, I have some pixels in an image that I need to zero out. By that I mean I want the RGBA values to all be set to 0.
I attempted to:
use the rectangular select tool to select the group of pixels
use bucket fill to set the pixels to black with opacity set to 0.0
Then, to verify it was done correctly, I use the color picker to test the value of the rectangle I just filled.
Unfortunately, it seems to just contain the previous value. What am I missing here?
The "opacity" of the bucket-fill is the opacity of the paint, not the opacity of the resulting pixels. In other words the less opaque it is, the less visible the result. What you want to do is bucket-fill selection with black, then [delete].
hi this is an image i attached. Actually i want to build a system in which i want to move the car button (showing in image) to different specified positions(showing on the right) and at each position i want to replace the car image with different one(like truck, train). is there any way to do this ?
Link to the image:-
https://drive.google.com/file/d/0B-TGzvOW0sr9Wlk3T25DYWZlOGs/view
yes there is always a way to do it :-)
so create a UIView subclass which has two UIImageViews. 1st UIImageView can be the horizontal line. and the second UIImageView can be the with the car. you then move the UIImageView horizontally as you wish and set different images while changing the position.
edit:
1. moving an UI element can be done with resetting the frame of UI element.
for example if an image was at position (x,y, width, height) and you want to move 20 points to the right then it will be (x + 20, y, width, height)
if you use auto layout then you can just change the constant of your x-constraint in this case.
edit 2 :
you can use (Tap/Pan) Gesture recogniser. you will get the exact position and as well as the velocity with different state (gesture started/ended/changed).
I referred to following article. What I actually need to draw is concentric/ Concrete circles with an effect as shown in image below.
I am finding it difficult to a) Draw the white streaks radially b) Find some key terms to search for related articles to proceed further on this.
Any hint or link to read about this will be of great help.
Try these
Metallic Knob
Metallic Knob 2
http://maniacdev.com/2012/06/ios-source-code-example-making-reflective-metallic-buttons-like-the-music-app
This is a tutorial on making reflective metal buttons. You can apply the techniques from the source code to whatever object you're trying to make. The source code is found here on github. I just googled "ios objective c metal effect" because that's what you're trying to do, right? The metal effect appears in concentric circles and changes as you tilt your phone, just as the iOS6 music slider does.
I don't have any code for you but the idea is actually quite simple. You're drawing a number of lines radiating from a single, central point (say 50,50) to four different sets of points. First set is for x = 0 to 100, y = 0. Second set is for y = 0 to 100, x = 0. Third set is for x = 0 to 100, y = 100. Fourth set is for y = 0 to 100, x = 100. And for each step you need to either change the colour from white to black or white to grey in increments or use a look up table with your colour values in it.
So i have a custom UISlider. It's vertical (i did it with the +270° technic). I have 3 images, respectively for the minimum value, maximum value and for the thumb. Everything seems good but i have problems with the extrema values, as you can observe on the screen capture (even though it's a little dark).
The slider on the left is perfect ! Both end of the sliders show the images perfectly and the cursor (thumb) is perfectly cutting the slider in 2.
The other two sliders on the right shows a similar issue. We can see that, when in extrema value, the cursor is not well located (there shouldn't be any part of the image below or above the middle of the cursor !) Oo
More to that, let's look at the right slider (with minimum value). We can see that image has been cut on the bottom ! Indeed it should be close. It's the same thing for the maximum value, the image looks like it's been cut.
I looked at the bounds of the slider view by touching it at both ends and looking at its coordinates. The slider was defined with a height of 300 but i can perform touches at coordinate 307, or -6 !!! I don't really understand why..
For more information, coordinates form 300 to 310 represents the maximum value i defined and negative coordinates (from 0 to -10) represents the minimum value.
-> So We can notice there's a difference of 10 at both ends.
Please help ! :s