Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Can't scale images #3

Open
tonycpsu opened this issue Oct 8, 2012 · 11 comments
Open

Can't scale images #3

tonycpsu opened this issue Oct 8, 2012 · 11 comments

Comments

@tonycpsu
Copy link

tonycpsu commented Oct 8, 2012

Is it possible to use Scale() to up-scale images? I tried using Scale() with makeimage() and Image() but it doesn't seem to do anything.

@ajstarks
Copy link
Owner

ajstarks commented Oct 8, 2012

Image scaling is not supported at this time. If it were what API would you propose?

@tonycpsu
Copy link
Author

tonycpsu commented Oct 8, 2012

Well, with the current API design where everything returns void, I guess I would just expect the Scale() function to up-scale whatever's on the canvas at the time. Going forward, I think that returning some sort of context structure back to the user would make things like this easier -- e.g., Image() and makeimage() would return a context back to the caller, then the caller can call Scale(), Rotate(), etc. on those "objects".

@tonycpsu
Copy link
Author

Here's an idea -- instead of directly adding support for scaling images, what about giving users a canvas-like object (opaque pointer) that they can then scale, rotate, translate, etc. and then place within other canvases? I think this is how other 2D toolkits like MagickWand and GD do it. In fact, even without scaling, the ability to compose canvases within canvases would be very useful on its own.

@jamazerto
Copy link

You can scale images in OpenVG, OpenVG just uses different matrices to store the transformation of paths and images. For example that code would do it and then reset the matrix you're currently modifying to the one applied to paths.

vgSeti(VG_MATRIX_MODE, VG_MATRIX_IMAGE_USER_TO_SURFACE);
Scale(scale, scale);
vgSeti(VG_MATRIX_MODE, VG_MATRIX_PATH_USER_TO_SURFACE);

@klkl140
Copy link

klkl140 commented Oct 7, 2014

After playing some hours with openvg I found the following solution. A change in libshapes.c.

void Image(VGfloat x, VGfloat y, int w, int h, char *filename) {
VGImage img = createImageFromJpeg(filename);
#if 0 //vgSetPixels paints directly without scale and transform
vgSetPixels(x, y, img, 0, 0, w, h);
#else //vgDrawImage is better
vgSeti(VG_MATRIX_MODE, VG_MATRIX_IMAGE_USER_TO_SURFACE);
vgTranslate(x, y);
vgDrawImage(img);
vgTranslate(-x, -y);
vgSeti(VG_MATRIX_MODE, VG_MATRIX_PATH_USER_TO_SURFACE);
#endif
vgDestroyImage(img);
}

It does break older code, because this way translate and scale do work on images too.

Hope it helps someone...
Greetings Klaus

@LucaSoldi
Copy link

Hi klkl140 I have the same problem with scaling images, I modified libshape.c with your code but the image is not scaled :( Any suggestions?

Thanks!!

EDIT: Solve :)

@gurtajs4
Copy link

HI @LucaSoldi and @klkl140 ,

I am looking for a solution to scale the image from res 1920x1080 to 320x240.
@LucaSoldi you did commented above that the in first try it didn't worked for you but later you solved it.
Can you guys provide some insight, perhaps some code sharing on how this is done.

Regards,
Gurtaj

@klkl140
Copy link

klkl140 commented May 13, 2017 via email

@gurtajs4
Copy link

Hi @klkl140 ,
I was going through openvg bug list and found you comments.

https://github.com/ajstarks/openvg/issues/3

When I do the change in libshapes.c.

void Image(VGfloat x, VGfloat y, int w, int h, char *filename) {
VGImage img = createImageFromJpeg(filename);
#if 0 //vgSetPixels paints directly without scale and transform
vgSetPixels(x, y, img, 0, 0, w, h);
#else //vgDrawImage is better
vgSeti(VG_MATRIX_MODE, VG_MATRIX_IMAGE_USER_TO_SURFACE);
vgTranslate(x, y);
vgDrawImage(img);
vgTranslate(-x, -y);
vgSeti(VG_MATRIX_MODE, VG_MATRIX_PATH_USER_TO_SURFACE);
#endif
vgDestroyImage(img);
}

I always see full size Image.

Thanks,
Gurtaj

@paeryn
Copy link

paeryn commented May 13, 2017

Are you scaling the VG_MATRIX_IMAGE_USER_TO_SURFACE matrix? If not then drawn images won't get scaled (see jamazerto's post above). By default the matrix to be altered is VG_MATRIX_PATH_USER_TO_SURFACE which only affects how paths are transformed.

OpenVG uses 5 separate matrices, VG_MATRIX_PATH_USER_TO_SURFACE to transform paths (which are used to draw the various shapes) and VG_MATRIX_IMAGE_USER_TO_SURFACE to transform images (the others transform the fill and stroke paints and text glyphs).

@gurtajs4
Copy link

HI @paeryn
As mentioned in the code snippet above I am using exact these changes in libshape.c

void Image(VGfloat x, VGfloat y, int w, int h, char *filename) {
VGImage img = createImageFromJpeg(filename);
#if 0 //vgSetPixels paints directly without scale and transform
vgSetPixels(x, y, img, 0, 0, w, h);
#else //vgDrawImage is better
vgSeti(VG_MATRIX_MODE, VG_MATRIX_IMAGE_USER_TO_SURFACE);
vgTranslate(x, y);
vgDrawImage(img);
vgTranslate(-x, -y);
vgSeti(VG_MATRIX_MODE, VG_MATRIX_PATH_USER_TO_SURFACE);
#endif
vgDestroyImage(img);
}

Remember I want to scale down the image from resolution 1920x1080 to 320x240.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
None yet
Projects
None yet
Development

No branches or pull requests

7 participants