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Code Issues Releases Wiki Activity

Add comments for the “rotate fix”

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This commit is contained in:
Keyon U
2018-08-22 18:03:02 +08:00
parent 48beb184df
commit 2bbcb8ca89
1 changed files with 40 additions and 4 deletions
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44
browser/main/lib/dataApi/attachmentManagement.js
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@@ -11,7 +11,12 @@ import i18n from 'browser/lib/i18n'
const STORAGE_FOLDER_PLACEHOLDER = ':storage'
const DESTINATION_FOLDER = 'attachments'
const PATH_SEPARATORS = escapeStringRegexp(path.posix.sep) + escapeStringRegexp(path.win32.sep)
/**
* @description
* Create a Image element to get the real size of image.
* @param {File} file the File object dropped.
* @returns {Promise<Image>} Image element created
*/
function getImage (file) {
return new Promise((resolve) => {
const reader = new FileReader()
@@ -24,29 +29,54 @@ function getImage (file) {
})
}
/**
* @description
* Get the orientation info from iamges's EXIF data.
* case 1: The 0th row is at the visual top of the image, and the 0th column is the visual left-hand side.
* case 2: The 0th row is at the visual top of the image, and the 0th column is the visual right-hand side.
* case 3: The 0th row is at the visual bottom of the image, and the 0th column is the visual right-hand side.
* case 4: The 0th row is at the visual bottom of the image, and the 0th column is the visual left-hand side.
* case 5: The 0th row is the visual left-hand side of the image, and the 0th column is the visual top.
* case 6: The 0th row is the visual right-hand side of the image, and the 0th column is the visual top.
* case 7: The 0th row is the visual right-hand side of the image, and the 0th column is the visual bottom.
* case 8: The 0th row is the visual left-hand side of the image, and the 0th column is the visual bottom.
* Other: reserved
* ref: http://sylvana.net/jpegcrop/exif_orientation.html
* @param {File} file the File object dropped.
* @returns {Promise<Number>} Orientation info
*/
function getOrientation (file) {
const getData = arrayBuffer => {
const view = new DataView(arrayBuffer)
// Not start with SOI(Start of image) Marker return fail value
if (view.getUint16(0, false) !== 0xFFD8) return -2
const length = view.byteLength
let offset = 2
while (offset < length) {
const marker = view.getUint16(offset, false)
offset += 2
// Loop and seed for APP1 Marker
if (marker === 0xFFE1) {
// return fail value if it isn't EXIF data
if (view.getUint32(offset += 2, false) !== 0x45786966) {
return -1
}
// Read TIFF header,
// First 2bytes defines byte align of TIFF data.
// If it is 0x4949="II", it means "Intel" type byte align.
// If it is 0x4d4d="MM", it means "Motorola" type byte align
const little = view.getUint16(offset += 6, false) === 0x4949
offset += view.getUint32(offset + 4, little)
const tags = view.getUint16(offset, little)
const tags = view.getUint16(offset, little) // Get TAG number
offset += 2
for (let i = 0; i < tags; i++) {
// Loop to find Orientation TAG and return the value
if (view.getUint16(offset + (i * 12), little) === 0x0112) {
return view.getUint16(offset + (i * 12) + 8, little)
}
}
} else if ((marker & 0xFF00) !== 0xFF00) {
} else if ((marker & 0xFF00) !== 0xFF00) { // If not start with 0xFF, not a Marker
break
} else {
offset += view.getUint16(offset, false)
@@ -60,7 +90,13 @@ function getOrientation (file) {
reader.readAsArrayBuffer(file.slice(0, 64 * 1024))
})
}
/**
* @description
* Rotate image file to correct direction.
* Create a canvas and draw the image with correct direction, then export to base64 format.
* @param {*} file the File object dropped.
* @return {String} Base64 encoded image.
*/
function fixRotate (file) {
return Promise.all([getImage(file), getOrientation(file)])
.then(([img, orientation]) => {