private PreviewItemDrawingParams computePreviewItemDrawingParams(
int index, PreviewItemDrawingParams params) {
index = NUM_ITEMS_IN_PREVIEW - index - 1;
float r = (index * 1.0f) / (NUM_ITEMS_IN_PREVIEW - 1);
float scale = (1 - PERSPECTIVE_SCALE_FACTOR * (1 - r));
float offset = (1 - r) * mMaxPerspectiveShift;
float scaledSize = scale * mBaselineIconSize;
float scaleOffsetCorrection = (1 - scale) * mBaselineIconSize;
// We want to imagine our coordinates from the bottom left, growing up and to the
// right. This is natural for the x-axis, but for the y-axis, we have to invert things.
float transY = mAvailableSpaceInPreview - (offset + scaledSize + scaleOffsetCorrection);
float transX = offset + scaleOffsetCorrection;
float totalScale = mBaselineIconScale * scale;
final int overlayAlpha = (int) (80 * (1 - r));
if (params == null) {
params = new PreviewItemDrawingParams(transX, transY, totalScale, overlayAlpha);
} else {
params.transX = transX;
params.transY = transY;
params.scale = totalScale;
params.overlayAlpha = overlayAlpha;
}
return params;
}
