Add support for flip/flop/rotate after auto-orient

fixes #4144

docs/api-operation.md

@@ -15,8 +15,9 @@ Mirroring is supported and may infer the use of a flip operation.
 
 The use of `rotate` without an angle will remove the EXIF `Orientation` tag, if any.
 
-Only one rotation can occur per pipeline.
+Only one rotation can occur per pipeline (aside from an initial call without
-Previous calls to `rotate` in the same pipeline will be ignored.
+arguments to orient via EXIF data). Previous calls to `rotate` in the same
+pipeline will be ignored.
 
 Multi-page images can only be rotated by 180 degrees.
 
@@ -60,6 +61,22 @@ const resizeThenRotate = await sharp(input)
 ```
 
 
+## autoOrient
+> autoOrient() ⇒ <code>Sharp</code>
+
+Alias for calling `rotate()` with no arguments, which orients the image based
+on EXIF orientsion.
+
+This operation is aliased to emphasize its purpose, helping to remove any
+confusion between rotation and orientation.
+
+
+**Example**  
+```js
+const output = await sharp(input).autoOrient().toBuffer();
+```
+
+
 ## flip
 > flip([flip]) ⇒ <code>Sharp</code>
 

lib/index.d.ts

@@ -364,24 +364,72 @@ declare namespace sharp {
         //#region Operation functions
 
         /**
-         * Rotate the output image by either an explicit angle or auto-orient based on the EXIF Orientation tag.
+         * Rotate the output image by either an explicit angle
+         * or auto-orient based on the EXIF `Orientation` tag.
          *
-         * If an angle is provided, it is converted to a valid positive degree rotation. For example, -450 will produce a 270deg rotation.
+         * If an angle is provided, it is converted to a valid positive degree rotation.
+         * For example, `-450` will produce a 270 degree rotation.
          *
-         * When rotating by an angle other than a multiple of 90, the background colour can be provided with the background option.
+         * When rotating by an angle other than a multiple of 90,
+         * the background colour can be provided with the `background` option.
          *
-         * If no angle is provided, it is determined from the EXIF data. Mirroring is supported and may infer the use of a flip operation.
+         * If no angle is provided, it is determined from the EXIF data.
+         * Mirroring is supported and may infer the use of a flip operation.
          *
-         * The use of rotate implies the removal of the EXIF Orientation tag, if any.
+         * The use of `rotate` without an angle will remove the EXIF `Orientation` tag, if any.
          *
-         * Method order is important when both rotating and extracting regions, for example rotate(x).extract(y) will produce a different result to extract(y).rotate(x).
+         * Only one rotation can occur per pipeline (aside from an initial call without
-         * @param angle angle of rotation. (optional, default auto)
+         * arguments to orient via EXIF data). Previous calls to `rotate` in the same
-         * @param options if present, is an Object with optional attributes.
+         * pipeline will be ignored.
+         *
+         * Multi-page images can only be rotated by 180 degrees.
+         *
+         * Method order is important when rotating, resizing and/or extracting regions,
+         * for example `.rotate(x).extract(y)` will produce a different result to `.extract(y).rotate(x)`.
+         *
+         * @example
+         * const pipeline = sharp()
+         *   .rotate()
+         *   .resize(null, 200)
+         *   .toBuffer(function (err, outputBuffer, info) {
+         *     // outputBuffer contains 200px high JPEG image data,
+         *     // auto-rotated using EXIF Orientation tag
+         *     // info.width and info.height contain the dimensions of the resized image
+         *   });
+         * readableStream.pipe(pipeline);
+         *
+         * @example
+         * const rotateThenResize = await sharp(input)
+         *   .rotate(90)
+         *   .resize({ width: 16, height: 8, fit: 'fill' })
+         *   .toBuffer();
+         * const resizeThenRotate = await sharp(input)
+         *   .resize({ width: 16, height: 8, fit: 'fill' })
+         *   .rotate(90)
+         *   .toBuffer();
+         *
+         * @param {number} [angle=auto] angle of rotation.
+         * @param {Object} [options] - if present, is an Object with optional attributes.
+         * @param {string|Object} [options.background="#000000"] parsed by the [color](https://www.npmjs.org/package/color) module to extract values for red, green, blue and alpha.
+         * @returns {Sharp}
          * @throws {Error} Invalid parameters
-         * @returns A sharp instance that can be used to chain operations
          */
         rotate(angle?: number, options?: RotateOptions): Sharp;
 
+        /**
+         * Alias for calling `rotate()` with no arguments, which orients the image based
+         * on EXIF orientsion.
+         *
+         * This operation is aliased to emphasize its purpose, helping to remove any
+         * confusion between rotation and orientation.
+         *
+         * @example
+         * const output = await sharp(input).autoOrient().toBuffer();
+         *
+         * @returns {Sharp}
+         */
+        autoOrient(): Sharp
+  
         /**
          * Flip the image about the vertical Y axis. This always occurs after rotation, if any.
          * The use of flip implies the removal of the EXIF Orientation tag, if any.

lib/operation.js

@@ -32,8 +32,9 @@ const vipsPrecision = {
  *
  * The use of `rotate` without an angle will remove the EXIF `Orientation` tag, if any.
  *
- * Only one rotation can occur per pipeline.
+ * Only one rotation can occur per pipeline (aside from an initial call without
- * Previous calls to `rotate` in the same pipeline will be ignored.
+ * arguments to orient via EXIF data). Previous calls to `rotate` in the same
+ * pipeline will be ignored.
  *
  * Multi-page images can only be rotated by 180 degrees.
  *
@@ -92,6 +93,22 @@ function rotate (angle, options) {
   return this;
 }
 
+/**
+ * Alias for calling `rotate()` with no arguments, which orients the image based
+ * on EXIF orientsion.
+ *
+ * This operation is aliased to emphasize its purpose, helping to remove any
+ * confusion between rotation and orientation.
+ *
+ * @example
+ * const output = await sharp(input).autoOrient().toBuffer();
+ *
+ * @returns {Sharp}
+ */
+function autoOrient () {
+  return this.rotate();
+}
+
 /**
  * Mirror the image vertically (up-down) about the x-axis.
  * This always occurs before rotation, if any.
@@ -935,6 +952,7 @@ function modulate (options) {
  */
 module.exports = function (Sharp) {
   Object.assign(Sharp.prototype, {
+    autoOrient,
     rotate,
     flip,
     flop,

src/pipeline.cc

@@ -67,10 +67,10 @@ class PipelineWorker : public Napi::AsyncWorker {
         // Rotate and flip image according to Exif orientation
         std::tie(autoRotation, autoFlip, autoFlop) = CalculateExifRotationAndFlip(sharp::ExifOrientation(image));
         image = sharp::RemoveExifOrientation(image);
-      } else {
-        rotation = CalculateAngleRotation(baton->angle);
       }
 
+      rotation = CalculateAngleRotation(baton->angle);
+
       // Rotate pre-extract
       bool const shouldRotateBefore = baton->rotateBeforePreExtract &&
         (rotation != VIPS_ANGLE_D0 || autoRotation != VIPS_ANGLE_D0 ||
@@ -92,18 +92,14 @@ class PipelineWorker : public Napi::AsyncWorker {
           image = image.rot(autoRotation);
           autoRotation = VIPS_ANGLE_D0;
         }
-        if (autoFlip) {
+        if (autoFlip != baton->flip) {
           image = image.flip(VIPS_DIRECTION_VERTICAL);
           autoFlip = false;
-        } else if (baton->flip) {
-          image = image.flip(VIPS_DIRECTION_VERTICAL);
           baton->flip = false;
         }
-        if (autoFlop) {
+        if (autoFlop != baton->flop) {
           image = image.flip(VIPS_DIRECTION_HORIZONTAL);
           autoFlop = false;
-        } else if (baton->flop) {
-          image = image.flip(VIPS_DIRECTION_HORIZONTAL);
           baton->flop = false;
         }
         if (rotation != VIPS_ANGLE_D0) {
@@ -396,11 +392,11 @@ class PipelineWorker : public Napi::AsyncWorker {
         image = image.rot(autoRotation);
       }
       // Mirror vertically (up-down) about the x-axis
-      if (baton->flip || autoFlip) {
+      if (baton->flip != autoFlip) {
         image = image.flip(VIPS_DIRECTION_VERTICAL);
       }
       // Mirror horizontally (left-right) about the y-axis
-      if (baton->flop || autoFlop) {
+      if (baton->flop != autoFlop) {
         image = image.flip(VIPS_DIRECTION_HORIZONTAL);
       }
       // Rotate post-extract 90-angle