ngryman/ribs

/*!
 * ribs
 * Copyright (c) 2013-2014 Nicolas Gryman <ngryman@gmail.com>
 * LGPL Licensed
 */

'use strict';

/**
 * Module dependencies.
 */

var utils = require('./utils');

/**
 * Hooks.
 */

var hooks = {};

/**
 * Resize constraints hook.
 * Applies default constraints to given `width` and `height` for a resize operation.
 * It ensures that aspect ratio is preserved and only allows downscale.
 * It lets the user customize how constraints are computed by RIBS.
 *
 * @param {object} params - Parameters to hook.
 * @param {(number|string)} params.width - Width after resize.
 * @param {(number|string)} params.height - Height after resize.
 * @param {Image} image - Image to process.
 */
hooks.resizeConstraintsHook = function(params, image) {
    var dstWidth = params.width,
        dstHeight = params.height,
        srcWidth = image.width,
        srcHeight = image.height;

    // treat formulas
    if ('string' == typeof dstWidth)
        dstWidth = utils.computeFormula(dstWidth, srcWidth);
    if ('string' == typeof dstHeight)
        dstHeight = utils.computeFormula(dstHeight, srcHeight);

    // treat null values
    if (null == dstWidth)  dstWidth  = 0;
    if (null == dstHeight) dstHeight = 0;

    // clamping and adjustments
    //  - 0 dest size is assigned to src size
    //  - negative dest size is src size - 2 * src size
    //  - clamp upscale
    if (0 === dstWidth)
        dstWidth = srcWidth;
    else if (dstWidth < 0)
        dstWidth = srcWidth + 2 * dstWidth;
    else if (dstWidth > srcWidth)
        dstWidth = srcWidth;
    if (0 === dstHeight)
        dstHeight = srcHeight;
    else if (dstHeight < 0)
        dstHeight = srcHeight + 2 * dstHeight;
    else if (dstHeight > srcHeight)
        dstHeight = srcHeight;

    // ratio constraints applied to the smaller size
    var ratio = srcWidth / srcHeight;
    if (dstWidth / srcWidth <= dstHeight / srcHeight)
        dstHeight = dstWidth / ratio;
    else
        dstWidth = dstHeight * ratio;

    // rounding
    dstWidth = Math.round(dstWidth);
    dstHeight = Math.round(dstHeight);

    // assign new values
    params.width = dstWidth;
    params.height = dstHeight;
};

/**
 * Crop constraints hook.
 * Applies default constraints to given `width`, `height`, `x`, `y` and `anchor` for a crop operation.
 * It ensures that cropping is centered when no `x`, `y` and `anchor` are provided and clamps the region to the image size.
 * if `anchor` is specified without `x` and `y`, it deducts those values from original image size.
 * If `x` and `y` are specified without `anchor`, it crops taking `x` and `y` as center.
 * If `anchor`, `x` and `y` are specified, it crops taking `x` and `y` as reference point. Cropping direction is then
 * deducted from `anchor`.
 * It lets the user customize how constraints are computed by RIBS.
 *
 * @param {object} params - Parameters to hook.
 * @param {(number|string)} params.width - Width after crop.
 * @param {(number|string)} params.height - Height after crop.
 * @param {(number|string)} params.x - x coordinate from where to crop.
 * @param {(number|string)} params.y - y coordinate from where to crop.
 * @param {(string)} params.anchor - Anchor point form where to crop.
 * @param {(string)} params.gravity - Direction of the crop.
 * @param {image} image - Image to process.
 */
hooks.cropConstraintsHook = function(params, image) {
    var dstWidth = params.width,
        dstHeight = params.height,
        anchor = params.anchor,
        gravity = params.gravity,
        srcWidth = image.width,
        srcHeight = image.height;

    // treat formulas
    if ('string' == typeof dstWidth)
        dstWidth = utils.computeFormula(dstWidth, srcWidth);
    if ('string' == typeof dstHeight)
        dstHeight = utils.computeFormula(dstHeight, srcHeight);
    if ('string' == typeof params.x)
        params.x = utils.computeFormula(params.x, srcHeight);
    if ('string' == typeof params.y)
        params.y = utils.computeFormula(params.y, srcHeight);

    // treat possible null values
    if (null == dstWidth)  dstWidth  = 0;
    if (null == dstHeight) dstHeight = 0;
    if (null == params.x) params.x = Math.round(srcWidth / 2);
    if (null == params.y) params.y = Math.round(srcHeight / 2);

    // compute anchor point coordinates
    if (anchor)
        utils.computeAnchor(anchor, srcWidth, srcHeight, params);

    // default gravity to anchor by default
    if (anchor && !gravity) gravity = anchor;

    // compute crop region origin
    utils.computeRegionOrigin(gravity, dstWidth, dstHeight, params.x, params.y, params);

    // adjustments
    //  - 0 dest size is assigned to src size
    //  - negative dest size is src size - 2 * src size
    if (0 === dstWidth)
        dstWidth = srcWidth;
    else if (dstWidth < 0)
        dstWidth = srcWidth + 2 * dstWidth;
    else if (dstWidth > srcWidth)
        dstWidth = srcWidth;
    if (0 === dstHeight)
        dstHeight = srcHeight;
    else if (dstHeight < 0)
        dstHeight = srcHeight + 2 * dstHeight;
    else if (dstHeight > srcHeight)
        dstHeight = srcHeight;

    // additional adjustments / clamping
    if (params.x + dstWidth > srcWidth)
        params.x -= params.x + dstWidth - srcWidth;
    if (params.y + dstHeight > srcHeight)
        params.y -= params.y + dstHeight - srcHeight;
    params.x = utils.clamp(params.x, 0, srcWidth - 1);
    params.y = utils.clamp(params.y, 0, srcHeight - 1);

    // rounding
    dstWidth = Math.round(dstWidth);
    dstHeight = Math.round(dstHeight);
    params.x = Math.round(params.x);
    params.y = Math.round(params.y);

    // assign new values
    params.width = dstWidth;
    params.height = dstHeight;
};

/**
 * Export.
 */

module.exports = hooks;