Develop Reference

AppCompatImageView displaying big image using ScaleType.CENTER and the use of padding

I have an image 3264x1836 and I display it in a custom AppCompatImageView having dimensions 1280x720. I want to preserve the image size so I use ScaleType.CENTER, but I also want that its top-left corner is positioned at the coordinates 0,0 of my custom view, so I set the padding left and top accordingly.
Now, to achieve that I had to use 3264-1280 (the difference between the widths) as left padding and 1836-720 (the difference between the heights) as top padding while, in my opinion, these values should be both divided by 2.
Can somebody explain why?

It is likely that you are breaking the AppCompatImageView code by asking it to do something that wasn't anticipated or tested.
While the above could still be true, the padding that you are applying is correct. Here are the calculations:
For simplicity, let's take a look at the left padding needed to shift the graphic. The same sort of calculations will work for the top padding.
The width of the graphic is greater than the width of the ImageView.
d = wgraphic - wimageview
If the graphic is centered in the ImageView, then the overhang on the left and right sides will be 1/2 the difference in widths.
s = d / 2
The graphic is centered within the padding of the ImageView. The amount of padding that has to be specified must be just enough to shift the center of the graphic by the amount s.
The initial center of the ImageView without padding is
ci = wimageview / 2
The shifted center with left padding ( p ) is
cs = p + (wimageview - p) / 2
So,
s = cs - ci = p + (wimageview - p) / 2 - (wimageview / 2)
Solving for the padding needed for a shift of s we get p = 2s = d. In other words, the padding we need is twice the shift required which is what you are seeing.
A fix that doesn't involve padding would be to specify
android:scaleType="matrix"
You should remove the padding. The new scale type will apply the identity matrix to the image and place it in the top/left corner without resizing.

Android finding the center of screen in terms of px

Currently, My goal is to place some images in an arrangement relative to the center of the screen. There is a varying number of images and locations, so I'd like to do this programmatically.
I am having trouble finding the center of the correct center of screen in terms of px. To test, I have tried placing an image at the center.
ImageView image = (ImageView)findViewById(R.id.imageView1);
Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
int width = size.x;
int height = size.y;
image.setPadding(width/2,height/2,0,0);
I understand that there is an offset since setting the padding should place the image's top left corner in the center. Even so, the image comes out as too low and too far right. What kind of issue could be causing this?

Padding set just the inner space between element's border and content. If element have also margins, they summarized. You can use only margins (paddings equals to 0) or only paddings (margins equals to 0). Also if you not interested in supporting android 2.3 and less, you can use setX() and setY() methods of View class.
I hope this help you.

Get size of 9-patch content area

In my app, I have a feature where you can put a frame around an image.
I use setBackground(Drawable) to apply the image of the frame to an ImageView. When the ImageView is clicked, I want to blow the content area (the image contained in the frame) up to the size of the screen. For this, I need to know the difference between the entire view and the content area, i.e. the thickness of the border.
Is there a way to get the size of the content area? (Accessing View.getWidth() for the ImageView gives content + border. I'm trying to get the border / padding.)

You can use:
Rect padding = new Rect();
view.getBackground().getPadding(padding);
int contentWidth = view.getWidth() - padding.left - padding.right;
int contentHeight = view.getHeight() - padding.top - padding.bottom;
If your background is a nine patch, the getPadding method will return the insets of the drawable

Here's an alternative approach:
The horizontal and vertical borders of the 9patch frame should not be stretched vertically and horizontally, respectively. Therefore you have constant width of the vertical border and height of the horizontal border. You can open the 9patch with any image editor that supports measuring and measure those lengths.
Use those values as margin or padding of the content view. Providing a single 9patch for all DPIs should work as the system would stretch it for higher DPIs but your padding/margin would be in DPs, so it should be the same size as the frame.

Problems with the width of the bitmap. The width is limited by the height of the screen

I'm creating a bitmap wich i need to use as background of a 320 width screen. The problem is that the bitmap is not getting the width i want. It is getting two empty spaces on the left and on the right. It is because it is fitting the height of the screen, but i dont want that, i want to force the bitmap to have the width i want. Doesn't matter if a portion of the height of the bitmap is out of the screen.
i need to force the width when i am adding the image to the layout, i mean that the image must be keep the aspect ratio, but the image must be higher than the height of the screen, and the image must be shown incomplete if the heigh of the image is higher than the height of the screen. Now this is not happening, because the layout is forcing the width to respect the image and show all the height of the image in the height of the screen, then i think the problem is on the layout rules
im creating the bitmap with:
View view;
Bitmap aux = Util.loadImage( filename ); //image loaded but with his original width
Bitmap image = Util.scaleBitmap(aux, 320); //scaling to 320
((ImageView)view).setImageBitmap( resource.image );
RelativeLayout.LayoutParams rlp = new RelativeLayout.LayoutParams( 320 , h );
rlp.addRule( RelativeLayout.CENTER_HORIZONTAL );
rlp.addRule( RelativeLayout.ALIGN_PARENT_TOP );
layout.addView( view , rlp );
What am i doing wrong?

Try using this:
((ImageView)view).setScaleType(ImageView.FitCenter);
To see more options see http://developer.android.com/reference/android/widget/ImageView.html#attr_android:scaleType

Since you don't care about the height you should use CENTER_CROP.
Define the scale type and then set the image.
CENTER_CROP - Scale the image uniformly (maintain the image's aspect
ratio) so that both dimensions (width and height) of the image will be
equal to or larger than the corresponding dimension of the view (minus
padding).

scaling/formatting multiple imagebutton array in Android

So I have this task to create a horizontal scrolling array of image buttons that are basically photo avatars of users. These avatars aren't constrained by aspect ratio or size, and so I've been playing with ways to scale them and format them. I've gotten them scaling via the scaletype="fitCenter" and using static width and height. But what I really want them to do is to butt up against one another. Currently if an image is taller than it is high, you get the kind of letterboxing but on the sides vs. the top (blank areas). I've tried all the different scaling values, wrapping each imagemap within a linearlayout, etc., but nothing I try seems to get rid of those (while displaying the entire image to scale). Is there any way to do this?

Just to reiterate what I think you're doing, you have three image scenarios:
Square image
Landscape image (wider than tall)
Portrait image (taller than wide)
Laying out a row of fixed-size ImageViews (or ImageButtons) using FIT_CENTER works great for what you need if all the images were either square or landscape, because the scaling will always make the image stretch to the horizontal bounds of the view (the largest dimension). However, with portrait images, the scaling causes the view to be inside the bounds of your fixed-size view so that the entire image height can be visible.
If you need to maintain the aspect ratio of the image, there really is no ScaleType to help with this because the logic would be circular (fit the view to the image, while simultaneously fitting the image to the view). The solution is to adjust the size (specifically, the width) of each ImageView to match what the image will be scaled to. Here's a sample of a factory method you might use to generate the ImageView to fit the image you want to put inside it. You could also modify this slightly to reset parameters on an existing ImageView if you like:
private ImageView getImageViewForThumbnail(Bitmap thumbnail) {
float viewHeight = //Your chosen fixed view height
float scale = ((float)thumbnail.getHeight()) / viewHeight;
float viewWidth = thumbnail.getHeight() / scale;
ImageView view = new ImageView(this);
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams((int)viewWidth, (int)viewHeight);
view.setLayoutParams(params);
view.setScaleType(ScaleType.FIT_XY);
view.setImageBitmap(thumbnail);
return view;
}
You're basically just calculating what the aspect width of the ImageView should be to match the fixed height you've chosen for all of them.
HTH

Use the scaleType fitXY, it stretches the image to the layout params you assigned, if the image has less dimensions and also shrinks the image to the layout params you assigned, if the image is large. The key point is to mention the image layout params to the imageView , that is the width and height of the image.