probe-image-size/lib/parse_sync/svg.js

Get image size without full download (JPG, GIF, PNG, WebP, BMP, TIFF, PSD)

'use strict'


function isWhiteSpace (chr) {
  return chr === 0x20 || chr === 0x09 || chr === 0x0D || chr === 0x0A
}

// Filter NaN, Infinity, < 0
function isFinitePositive (val) {
  return typeof val === 'number' && isFinite(val) && val > 0
}

function canBeSvg (buf) {
  var i = 0
  var max = buf.length

  // byte order mark, https://github.com/nodeca/probe-image-size/issues/57
  if (buf[0] === 0xEF && buf[1] === 0xBB && buf[2] === 0xBF) i = 3

  while (i < max && isWhiteSpace(buf[i])) i++

  if (i === max) return false
  return buf[i] === 0x3c /* < */
}


// skip `<?` (comments), `<!` (directives, cdata, doctype),
// looking for `<svg>` or `<NAMESPACE:svg>`
var SVG_HEADER_RE = /<[-_.:a-zA-Z0-9][^>]*>/

// test if the top level element is svg + optional namespace,
// used to skip svg embedded in html
var SVG_TAG_RE = /^<([-_.:a-zA-Z0-9]+:)?svg\s/

var SVG_WIDTH_RE = /[^-]\bwidth="([^%]+?)"|[^-]\bwidth='([^%]+?)'/
var SVG_HEIGHT_RE = /\bheight="([^%]+?)"|\bheight='([^%]+?)'/
var SVG_VIEWBOX_RE = /\bview[bB]ox="(.+?)"|\bview[bB]ox='(.+?)'/
var SVG_UNITS_RE = /in$|mm$|cm$|pt$|pc$|px$|em$|ex$/

function svgAttrs (str) {
  var width = str.match(SVG_WIDTH_RE)
  var height = str.match(SVG_HEIGHT_RE)
  var viewbox = str.match(SVG_VIEWBOX_RE)

  return {
    width: width && (width[1] || width[2]),
    height: height && (height[1] || height[2]),
    viewbox: viewbox && (viewbox[1] || viewbox[2])
  }
}


function units (str) {
  if (!SVG_UNITS_RE.test(str)) return 'px'

  return str.match(SVG_UNITS_RE)[0]
}


module.exports = function (data) {
  if (!canBeSvg(data)) return

  var str = ''

  for (var i = 0; i < data.length; i++) {
    // 1. We can't rely on buffer features
    // 2. Don't care about UTF16 because ascii is enougth for our goals
    str += String.fromCharCode(data[i])
  }

  // get top level element
  var svgTag = (str.match(SVG_HEADER_RE) || [''])[0]

  // test if top level element is <svg>
  if (!SVG_TAG_RE.test(svgTag)) return

  var attrs = svgAttrs(svgTag)
  var width = parseFloat(attrs.width)
  var height = parseFloat(attrs.height)

  // Extract from direct values

  if (attrs.width && attrs.height) {
    if (!isFinitePositive(width) || !isFinitePositive(height)) return

    return {
      width: width,
      height: height,
      type: 'svg',
      mime: 'image/svg+xml',
      wUnits: units(attrs.width),
      hUnits: units(attrs.height)
    }
  }

  // Extract from viewbox

  var parts = (attrs.viewbox || '').split(' ')
  var viewbox = {
    width: parts[2],
    height: parts[3]
  }
  var vbWidth = parseFloat(viewbox.width)
  var vbHeight = parseFloat(viewbox.height)

  if (!isFinitePositive(vbWidth) || !isFinitePositive(vbHeight)) return
  if (units(viewbox.width) !== units(viewbox.height)) return

  var ratio = vbWidth / vbHeight

  if (attrs.width) {
    if (!isFinitePositive(width)) return

    return {
      width: width,
      height: width / ratio,
      type: 'svg',
      mime: 'image/svg+xml',
      wUnits: units(attrs.width),
      hUnits: units(attrs.width)
    }
  }

  if (attrs.height) {
    if (!isFinitePositive(height)) return

    return {
      width: height * ratio,
      height: height,
      type: 'svg',
      mime: 'image/svg+xml',
      wUnits: units(attrs.height),
      hUnits: units(attrs.height)
    }
  }

  return {
    width: vbWidth,
    height: vbHeight,
    type: 'svg',
    mime: 'image/svg+xml',
    wUnits: units(viewbox.width),
    hUnits: units(viewbox.height)
  }
}