Q:

Resize image to full width and variable height with Picasso

I have a listView with an adapter that contains ImageView of variable size (width and height). I need resize the pictures load with Picasso to the max width of layout and a variable height given by the aspect ratio of the picture.
I have checked this question:
Resize image to full width and fixed height with Picasso
The fit() works but I haven't found nothing to keep the aspect ratio of the picture.
This code partially works if I fixed the height in the layout of the adapter:
Picasso.with(this.context).load(message_pic_url)
.placeholder(R.drawable.profile_wall_picture)
.fit().centerInside()
.into(holder.message_picture);

But it generates blank spaces between the pictures of the listView because the pictures may be that not have that height.
Thanks in advance.

A:

As of Picasso 2.4.0, this operation is now directly supported.  Simply add a .resize() request with one of the dimensions as 0.  For example, to have a variable width, your call would become:
Picasso.with(this.context)
       .load(message_pic_url)
       .placeholder(R.drawable.profile_wall_picture)
       .resize(0, holder.message_picture.getHeight()),
       .into(holder.message_picture);

Note that this call uses .getHeight() and therefore assumes the message_picture has already been measured.  If that isn't the case, such as when you have inflated a new view in a ListAdapter, you can delay this call until after measurement by adding an OnGlobalLayoutListener to the view:
holder.message_picture.getViewTreeObserver()
      .addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            // Wait until layout to call Picasso
            @Override
            public void onGlobalLayout() {
                // Ensure we call this only once
                imageView.getViewTreeObserver()
                         .removeOnGlobalLayoutListener(this);

                Picasso.with(this.context)
                       .load(message_pic_url)
                       .placeholder(R.drawable.profile_wall_picture)
                       .resize(0, holder.message_picture.getHeight())
                       .into(holder.message_picture);
            }
        });

A:

I came across the same issue and it took me a while to track down a solution but I finally came across something that works for me.
Firstly I changed the Picasso call to
Picasso.with(this.context).load(message_pic_url)
.placeholder(R.drawable.profile_wall_picture)
.into(holder.message_picture);

Removing the fit and the centerInside. Next you need to add the following lines to the ImageView in your XML
android:scaleType="fitStart"
android:adjustViewBounds="true"

Hopefully it will work for you as well.

A:

Finally I solved it doing a transformation of Picasso, here is the snippet:
    Transformation transformation = new Transformation() {

        @Override
        public Bitmap transform(Bitmap source) {
            int targetWidth = holder.message_picture.getWidth();

            double aspectRatio = (double) source.getHeight() / (double) source.getWidth();
            int targetHeight = (int) (targetWidth * aspectRatio);
            Bitmap result = Bitmap.createScaledBitmap(source, targetWidth, targetHeight, false);
            if (result != source) {
                // Same bitmap is returned if sizes are the same
                source.recycle();
            }
            return result;
        }

        @Override
        public String key() {
            return "transformation" + " desiredWidth";
        }
    };

    mMessage_pic_url = message_pic_url;

    Picasso.with(this.context)
        .load(message_pic_url)
        .error(android.R.drawable.stat_notify_error)
        .transform(transformation)
        .into(holder.message_picture, new Callback() {
            @Override
            public void onSuccess() {
                holder.progressBar_picture.setVisibility(View.GONE);
            }

            @Override
            public void onError() {
                Log.e(LOGTAG, "error");
                holder.progressBar_picture.setVisibility(View.GONE);
            }
    });

This line is for customize with your desired width:
int targetWidth = holder.message_picture.getWidth();

Additionally this snipped include Callback for loading hide and error drawable built-in Picasso.
If you need more information to debug any error, you MUST implement a custom listener (Picasso builder) beacuse the onError Callback information is "null". You only know that there is an error for UI behavior.
I hope this helps someone to save many hours.

