Androidpdfviewer: Mark a point on PDF and detect it on singleTabListener irrespective of Zoom and size of page

[SagarKhurana]

Thanks Guys for such a great library using PDFium in android. It makes it real easier to show pdf in android our own way.

I have tried all the possible methods to find out to match the drawn points on the pdf and the point where user have tapped.
Everything works fine if the zoom=1.0 i.e default value.
If I zoom in to the page, and click on the point which is visible, the single tap event gives me some different x,y. I understand this, so I have tried to implement below things, but still no success.

 float xPositionInRealScale = pdfView.toRealScale(-pdfView.getCurrentXOffset() + e.getX());
  float yPositionInRealScale = pdfView.toRealScale(-pdfView.getCurrentYOffset() + e.getY());

 float x = xPositionInRealScale / pdfView.getPageSize(currentPage).getWidth() * 100;
  float y = yPositionInRealScale / pdfView.getPageSize(currentPage).getHeight() * 100;

and applying same method to my x,y points which are saved in db. If they match or are close by the pop-up is shown.

I tried to undersand this PR but unable to use it in my code.

your help is really appreciated.

[xiasenhai]

try this:

float scale = get current page scale;
float x = e.getX();
float y = e.getY();
PointF pageTranslate = find page current translation;
float sourceX =( x - pageTranslate.x) / scale;
float sourceY = (y - pageTranslate.y) / scale;

PdfDocument doc = get PdfDocument instance;
PdfiumCore core = get PdfiumCore instance;
int startX = 0;
int startY = 0;
int sizeX = get page width;
int sizeY = get page height;
int rotate = 0;
PointF mapped = core. mapDeviceCoordsToPage(doc, pageIndex, startX, startY, sizeX,
                                            sizeY, rotate, sourceX, sourceY);

[SagarKhurana]

@xiasenhai thanks for your reply.
I cannot find the method "mapDeviceCoordsToPage" in the class PDFiumCore.
I see, that you did some commit, but those changes are not available in the recent project which I am using.
Version of pdfium-android: '1.9.0'

[Lucasq95]

@xiasenhai thanks for your reply.
I cannot find the method "mapDeviceCoordsToPage" in the class PDFiumCore.
I see, that you did some commit, but those changes are not available in the recent project which I am using.
Version of pdfium-android: '1.9.0'

@SagarKhurana were you able to access the method "mapDeviceCoordsToPage" ?
I've been trying but it seems that this method is exposed in a pull request which hasnt been merged. So it isnt available in Version of pdfium-android: '1.9.0'.

If you were able to found a workaround to this issue, please help me. I really need it for a project im working on.

Thanks!!

[SagarKhurana]

@Lucasq95 Sorry for the little late reply.
but Yes, I was able to resolve my issue with the below code.

        float xPositionInRealScale = pdfView.toRealScale(-pdfView.getCurrentXOffset() + e.getX());
        float yPositionInRealScale = pdfView.toRealScale(-pdfView.getCurrentYOffset() + e.getY());

        if (pdfView.isSwipeVertical()) {
            xPositionInRealScale = xPositionInRealScale - pdfView.pdfFile.getSecondaryPageOffset(currentPage, 1);
            yPositionInRealScale = yPositionInRealScale - pdfView.pdfFile.getPageOffset(currentPage, 1);
        } else {
            xPositionInRealScale = xPositionInRealScale - pdfView.pdfFile.getPageOffset(currentPage, 1);
            yPositionInRealScale = yPositionInRealScale - pdfView.pdfFile.getSecondaryPageOffset(currentPage, 1);
        }
        float xPer = xPositionInRealScale / pdfView.getPageSize(currentPage).getWidth() * 100;
        float yPer = yPositionInRealScale / pdfView.getPageSize(currentPage).getHeight() * 100;

`

So my requirement was to create the canvas point on pdf page and recognize it after user single tap on it.
I converted the x-axis and y-axis to the width and height %.
for example, if the point is marked at the center then it is 50%:x and 50%:y so it will work on any device irrespective of the size of the screen or zoom level. Using the current offset and page offset I have made sure of that.

Hope this helps,
Let me know if you have any other doubt.
Thanks.

[Lucasq95]

@SagarKhurana thanks a lot for the response. Thats a really interesting resolution.

In my case, i solved it by using mapDeviceCoordsToPage method. This method isnt available in version 1.9.0 of PdfiumAndroid because it only existed on a pull request that was closed for some reason, so i created my own fork of PdfiumAndroid and implemented the method as it was done in that pull request.
Then i also forked AndroidPdfViewer to integrate that method and it worked.

This forks are available in my profile but in the next days i will delete them and push some new forks with a cleaner code. If someone tries to use them, they are also available in jitpack so that you can add the dependency to the latest tag on gradle.

[benjinus]

Convert the screen touch point to pdf page coordinate:

    private PointF convertScreenPointToPdfPagePoint(MotionEvent e, PDFView pdfView) {

        float x = e.getX();
        float y = e.getY();

        PdfFile pdfFile = pdfView.pdfFile;
        if (pdfFile == null) {
            return null;
        }
        float mappedX = -pdfView.getCurrentXOffset() + x;
        float mappedY = -pdfView.getCurrentYOffset() + y;
        int page = pdfFile.getPageAtOffset(pdfView.isSwipeVertical() ? mappedY : mappedX, pdfView.getZoom());
        SizeF pageSize = pdfFile.getScaledPageSize(page, pdfView.getZoom());
        int pageX, pageY;
        if (pdfView.isSwipeVertical()) {
            pageX = (int) pdfFile.getSecondaryPageOffset(page, pdfView.getZoom());
            pageY = (int) pdfFile.getPageOffset(page, pdfView.getZoom());
        } else {
            pageY = (int) pdfFile.getSecondaryPageOffset(page, pdfView.getZoom());
            pageX = (int) pdfFile.getPageOffset(page, pdfView.getZoom());
        }

        return pdfFile.mapDeviceCoordsToPage(page, pageX, pageY, (int) pageSize.getWidth(),
                (int) pageSize.getHeight(), (int) mappedX, (int) mappedY);
    }

incase someone really need it.

mapDeviceCoordsToPage() can be found in @xiasenhai 's PR HERE

[LightSun]

@benjinus thanks