Imagemagick perspective and virtual pixels - image-manipulation

I'm trying to automatically straighten an image so that a grid is aligned with the picture.
However, whenever I do the manipulation there is a white border around the image.
Can anybody help me with this problem?

I managed to solve it, turns out I had some values the wrong way round, which forced virtual pixels to be made.

Related

detect coordinates of some element on image

Please tell me how to solve this problem.
Where to start and which way to go.
I have an image with some buttons :
How can i detect coordinates of blue round button for example?
The difficulty lies in the fact that these are not application buttons, but just a picture on the desktop.
I understand that this is a vast and complex question, but tell me at least the right way.
It will be useful to many people.
The first thing I can imagine is to do a desktop screen, and then try to detect pixels with blue color.
You don't need to do manual image detection because Apple's vision framework already does this. You can use it to detect rectangular regions, detect text, or recognize and image within an image, depending on your needs.
See Detecting Objects in Still Images

UITableViewCell Background stretching

I have a problem in Swift with UITableViewCell background image. Let's say that it shows quite fine one iPhone5 but on iPhone 6Plus it is stretch and thus it looks bad. This is probably due to Aspect fill or something which I really couldn't manage to change and achieve what I want so would be the best if someone could poke sample code I am providing as well as image how it should look, so anyone can check it out and maybe give me some hint or tip or sample code or even fixed demo version.
So here it is:
Note that on left side there is a curve (like half a circle) around right side of icon. On bigger phones or tablet, that curve gets super stretch thus completely destroying the look.
Demo code link
Thanks all in advance for any help. I am pretty stuck with this one.
You can stretch an image while preserving the aspect ratio of a portion of that image using slicing. Xcode offers a graphical interface for doing this. The idea is that you decide what parts of the image are allowed to stretch and which aren't.
https://developer.apple.com/library/ios/recipes/xcode_help-image_catalog-1.0/chapters/SlicinganImage.html

Unity sprites don't render properly

I recently came across a problem I can't solve which involves not being able to draw my sprites properly. I have tried a lot of different things and couldn't find any solution.
Here is how the image should look like in unity:
And here is how it actually looks like:
If someone could tell me how to fix this, I would be very grateful.
Presumably the top image is a screenshot of your image manipulation program, many of which use the chequerboard pattern to mean transparency. As such, the image you have exported is a gradient going from almost solid white at the bottom to transparent at the top. This is why the image appears as such in Unity.
Also, if you're wondering why the image appears as though it has bands of different colours, this is due to a problem called colour banding. This can be fixed by using a technique called Dither (which adds some noise to the image), but how you do so will depend on which image manipulation program you are using.

Cocos2D changes the colours in the last row of pixles in a sprite?

I have never seen this issue before, its very strange. Just wondering if anyone else has come across this too.
I have added a sprite to my game, its supposed to be the top left corner of a box to put text on to. I want to make it scalable without loosing anything so i have it broken up into sections. In the image above the one on top is the image itself, and then the one on the bottom is the image when its being drawn in the iPhone simulator.
Any idea why the last column of pixels on the right are altered? I have not scaled the image at all.
I don't know about Cocos2D, but in general terms what you've done here is to draw the image at a position that isn't an exact multiple of one pixel.
Consequently even without scaling you have resampled the image across a grid that doesn't coincide with the original image data, causing all pixels to be a bit off. It's just the right-hand edge is the most obvious case, since the resampling leaves you with a partial transparency here. But look at eg the two rows of purple pixels in the border: they're not the same, because your vertical alignment is off as well, causing a small amount of colour from the grey border below it to bleed into the lower row of purple.
Ok I actually figured it out this time. Cocos2D adds a bit of antialiasing to CCTextures. To stop it from doing this you need to call this:
[[mySprite texture] setAliasTexParameters];
to turn it back on you call this:
[[mySprite texture] setAntiAliasTexParameters];

UIImageView renders image differently to original

The image on the right is the one that I produced in photoshop. I then stripped all text and put it in an image view, as soon as I did that there was a change in colour and the vertical line lost it sharpness. Has anyone else run into a similar problem? What do I do?
alt text http://grab.by/1DuZ
Are the dimensions correct? Is the position of the image an integer? If these cases antialiasing will slightly blur your image.
One thing to be careful of is that if your image is an odd number of pixels in either dimension then centering it onscreen will cause it to be misaligned. Imagine if you had a 1x1 image (just one pixel) and tried to center it perfectly onscreen. It can't be done because the screen is an even number of pixels wide and high. This is why it's best to always use even dimensioned images whenever possible.