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@brendanw
Created August 4, 2015 03:58
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package com.cinemagraph;
import android.graphics.Matrix;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.ImageView;
import android.widget.RelativeLayout;
/**
*
* @author brendanw
* * Reminders about position:
* (1) When a page fills the screen its position is 0
* (2) When a page is drawn off the right side of the screen, its position is 1
* (3) When a page is drawn off the left side of the screen, its position is -1
*/
public class ParallaxTransformer implements ViewPager.PageTransformer {
private static final String TAG = ParallaxTransformer.class.getSimpleName();
@Override
public void transformPage(View view, float position) {
RelativeLayout root = (RelativeLayout) ((FrameLayout) view)
.getChildAt(0);
Button previewBtn = (Button) root.findViewById(R.id.preview_btn);
Button wallpaperBtn = (Button) root.findViewById(R.id.set_wallpaper_btn);
previewBtn.setAlpha(1.0f - (float)Math.sqrt(Math.abs(position)));
wallpaperBtn.setAlpha(1.0f - (float)Math.sqrt(Math.abs(position)));
ImageView imageView = (ImageView) root.getChildAt(0);
if (position < -1) {
} else if (position <= 1) {
Matrix matrix = new Matrix();
matrix.reset();
float viewWidth = imageView.getWidth();
float viewHeight = imageView.getHeight();
float intrinsicWidth = imageView.getDrawable().getIntrinsicWidth();
float intrinsicHeight = imageView.getDrawable().getIntrinsicHeight();
float newWidth = viewWidth;
float newHeight = viewHeight;
float scale = 0.0f;
/*
* if the difference in width is proportionally greater than difference in
* height (ex: 2.5 > 1.9) then scale the bitmap by the height factor
*/
if (intrinsicWidth / viewWidth > intrinsicHeight / viewHeight) {
scale = viewHeight / intrinsicHeight;
matrix.setScale(scale, scale);
newWidth = intrinsicWidth * scale;
}
/*
* else, scale the bitmap by the width factor
*/
else {
scale = viewWidth / intrinsicWidth;
matrix.setScale(scale, scale);
newHeight = intrinsicHeight * scale;
}
/* offset to center the view horizontally */
float xOffset = (viewWidth - newWidth) / 2;
/*
* strategy:
* 1) get pixels moved relative to the view frame (X)
* 2) move the bitmap 0.5f * X
*/
float xPos = -position * viewWidth * 0.5f + xOffset;
// IGNORE BELOW THIS LINE
float yPos = (viewHeight - newHeight) / 2;
matrix.postTranslate(xPos, yPos);
imageView.setScaleType(ImageView.ScaleType.MATRIX);
imageView.setImageMatrix(matrix);
} else {
}
}
}
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