feature: align cover svg to viewer

docs/documentation.md

@@ -144,7 +144,8 @@ import {
   ALIGN_RIGHT,
   ALIGN_TOP,
   ALIGN_BOTTOM,
-
+  ALIGN_COVER,
+
   INITIAL_VALUE
 } from 'react-svg-pan-zoom'
 ```

src/constants.js

@@ -22,5 +22,6 @@ export const ALIGN_LEFT = 'left';
 export const ALIGN_RIGHT = 'right';
 export const ALIGN_TOP = 'top';
 export const ALIGN_BOTTOM = 'bottom';
+export const ALIGN_COVER = 'cover';
 
 export const INITIAL_VALUE = {}

src/features/zoom.js

@@ -2,7 +2,7 @@ import {fromObject, scale, transform, translate} from 'transformation-matrix';
 
 import {
   ACTION_ZOOM, MODE_IDLE, MODE_ZOOMING,
-  ALIGN_CENTER, ALIGN_LEFT, ALIGN_RIGHT, ALIGN_TOP, ALIGN_BOTTOM
+  ALIGN_CENTER, ALIGN_LEFT, ALIGN_RIGHT, ALIGN_TOP, ALIGN_BOTTOM, ALIGN_COVER
 } from '../constants';
 import {decompose, getSVGPoint, set} from './common';
 import calculateBox from '../utils/calculateBox';
@@ -101,15 +101,16 @@ export function fitToViewer(value, SVGAlignX=ALIGN_LEFT, SVGAlignY=ALIGN_TOP) {
   let scaleY = viewerHeight / SVGHeight;
   let scaleLevel = Math.min(scaleX, scaleY);
 
-  const scaleMatrix = scale(scaleLevel, scaleLevel);
+  let scaleMatrix = scale(scaleLevel, scaleLevel);
 
   let translateX = -SVGMinX * scaleX;
   let translateY = -SVGMinY * scaleY;
 
-  // after fitting, SVG and the viewer will match in width (1) or in height (2)
-  if (scaleX < scaleY) {
-    //(1) match in width, meaning scaled SVGHeight <= viewerHeight
+ // after fitting, SVG and the viewer will match in width (1) or in height (2) or SVG will cover the container with preserving aspect ratio (0)
+ if (scaleX < scaleY) {
     let remainderY = viewerHeight - scaleX * SVGHeight;
+
+    //(1) match in width, meaning scaled SVGHeight <= viewerHeight
     switch(SVGAlignY) {
       case ALIGN_TOP:
         translateY = -SVGMinY * scaleLevel;
@@ -123,12 +124,20 @@ export function fitToViewer(value, SVGAlignX=ALIGN_LEFT, SVGAlignY=ALIGN_TOP) {
         translateY = remainderY - SVGMinY * scaleLevel;
       break;
 
+      case ALIGN_COVER:
+        scaleMatrix = scale(scaleY, scaleY); // (0) we must now match to short edge, in this case - height
+        let remainderX = viewerWidth - scaleY * SVGWidth; // calculate remainder in the other scale
+
+        translateX = SVGMinX + Math.round(remainderX / 2); // center by the long edge
+      break;
+
       default:
         //no op
     }
   } else {
-    //(2) match in height, meaning scaled SVGWidth <= viewerWidth
     let remainderX = viewerWidth - scaleY * SVGWidth;
+
+    //(2) match in height, meaning scaled SVGWidth <= viewerWidth
     switch(SVGAlignX) {
       case ALIGN_LEFT:
         translateX = -SVGMinX * scaleLevel;
@@ -142,12 +151,20 @@ export function fitToViewer(value, SVGAlignX=ALIGN_LEFT, SVGAlignY=ALIGN_TOP) {
         translateX = remainderX - SVGMinX * scaleLevel;
       break;
 
+      case ALIGN_COVER:
+        scaleMatrix = scale(scaleX, scaleX); // (0) we must now match to short edge, in this case - width
+        let remainderY = viewerHeight - scaleX * SVGHeight; // calculate remainder in the other scale
+
+        translateY = SVGMinY + Math.round(remainderY / 2); // center by the long edge
+      break;
+
       default:
         //no op
     }
   }
 
   const translationMatrix = translate(translateX, translateY);
+
   const matrix = transform(
     translationMatrix, //2
     scaleMatrix        //1

storybook/stories/DifferentSizesStory.jsx

@@ -7,6 +7,7 @@ import {
   ALIGN_LEFT,
   ALIGN_RIGHT,
   ALIGN_TOP,
+  ALIGN_COVER,
   UncontrolledReactSVGPanZoom
 } from '../../src/index';
 
@@ -34,12 +35,14 @@ export default class DifferentSizesStory extends Component {
       SVGAlignX: select('toolbarProps.SVGAlignX', {
         [ALIGN_LEFT]: ALIGN_LEFT,
         [ALIGN_CENTER]: ALIGN_CENTER,
-        [ALIGN_RIGHT]: ALIGN_RIGHT
+        [ALIGN_RIGHT]: ALIGN_RIGHT,
+        [ALIGN_COVER]: ALIGN_COVER,
       }, ALIGN_LEFT),
       SVGAlignY: select('toolbarProps.SVGAlignY', {
         [ALIGN_TOP]: ALIGN_TOP,
         [ALIGN_CENTER]: ALIGN_CENTER,
-        [ALIGN_BOTTOM]: ALIGN_BOTTOM
+        [ALIGN_BOTTOM]: ALIGN_BOTTOM,
+        [ALIGN_COVER]: ALIGN_COVER,
       }, ALIGN_TOP),
     }
 

test/features/zoom.spec.js

@@ -5,6 +5,7 @@ import {
   ALIGN_LEFT,
   ALIGN_RIGHT,
   ALIGN_TOP,
+  ALIGN_COVER,
   fitSelection,
   fitToViewer,
   MODE_IDLE,
@@ -105,7 +106,29 @@ describe("fitSelection", () => {
   test.todo('h<w')
 })
 
-describe("fitToViewer", () => {
+describe("fitToViewer rect > viewer", () => {
+    test("rect with w>h", () => {
+      const value = getDefaultValue(
+        200, 100,       //viewer 200x100
+        0, 0, 400, 400, //svg 400x400
+      )
+
+      const value1 = fitToViewer(value, ALIGN_COVER, ALIGN_COVER)
+      expect(testSVGBBox(value1)).toEqual([0, -50, 200, 150])
+    })
+
+    test("rect with w<h", () => {
+      const value = getDefaultValue(
+        100, 200,       //viewer 200x100
+        0, 0, 400, 400, //svg 400x400
+      )
+
+      const value1 = fitToViewer(value, ALIGN_COVER, ALIGN_COVER)
+      expect(testSVGBBox(value1)).toEqual([-50, 0, 150, 200])
+    })
+})
+
+describe("fitToViewer rect < viewer", () => {
   test("rect with w>h", () => {
     const value = getDefaultValue(
       200, 100,       //viewer 200x100
@@ -120,6 +143,9 @@ describe("fitToViewer", () => {
 
     const value3 = fitToViewer(value, ALIGN_RIGHT, ALIGN_TOP)
     expect(testSVGBBox(value3)).toEqual([100, 0, 200, 100])
+
+    const value4 = fitToViewer(value, ALIGN_COVER, ALIGN_COVER)
+    expect(testSVGBBox(value4)).toEqual([0, -50, 200, 150])
   })
 
   test("rect with w<h", () => {
@@ -136,6 +162,9 @@ describe("fitToViewer", () => {
 
     const value3 = fitToViewer(value, ALIGN_LEFT, ALIGN_BOTTOM)
     expect(testSVGBBox(value3)).toEqual([0, 100, 100, 200])
+
+    const value4 = fitToViewer(value, ALIGN_COVER, ALIGN_COVER)
+    expect(testSVGBBox(value4)).toEqual([-50, 0, 150, 200])
   })
 })