camera preview stretched at 7 inch touchscreen

[lee_w]

Hello pi camera fellows,

I am trying to get an unstretched preview image on my touch display.
Its the official 7 inch touchscreen.
It has an non-square aspect ratio.

With the following entries at the /boot/config.txt

framebuffer_width=800
framebuffer_height=444
framebuffer_aspect=-1

The normal screen content looks good.

But the preview of the camera module seems to be directly written to the display.
The preview is always stretched.

My question is: Is it possible to stretch the preview of the camera module ?

I am using the python module: picamera

Perhaps somebody has a hint for me.

All the best,
Lee

[6by9]

https://picamera.readthedocs.io/en/late ... rer.window
As the MMAL noaspect flag is not apparently set you should be able to stretch away to your hearts content.

[aBUGSworstnightmare]

From The MagPi Camera Essentials, page 98:

Preview position/size
--preview or -p (x,y,w,h)
Allows the user to define the size of the preview window (with w
and h values) and its location on the screen (x and y). Note that this
will be superimposed over the top of any other windows/graphics.
For instance, to set its top-left corner at (100, 100) and give it
dimensions of 300 × 200, use: -p 100,100,300,200.

[lee_w]

hello 6by9 and aBUGSworstnightmare,

thank you very much for the fast responses.
feels good not to be alone with this problem

i already have tested the window feature with python and the picamera module.
the window option seems not to strecht the content.

i have striped down the code to this.
perhaps i did not find the right flag to avoid scaling with the default ratio.

all the best,
lee

import time

from picamera import PiCamera

camera = PiCamera()
camera.resolution = (1920,1080)

time.sleep(1)
camera.preview_fullscreen=False
camera.preview_window=(100, 100, 800, 100)
camera.start_preview(resolution=(800, 480))
time.sleep(11111)

[lee_w]

Hello pi cam fellows,

I also tested the terminal command:

raspistill -p 100,100,300,200

Its the same result as using python.
The preview image is cropped, but not streched.

For now i see no chance to display an unstreched image on the official 7 inch touchscreen.
Its crazy that the screen has a non squared pixel size ....

Perhaps in the future a ratio flag for the preview output of the camera would be nice.
I sthis the right place to post e feature request ?

All the best,
Lee

[jamesh]

Hello pi cam fellows,

I also tested the terminal command:

raspistill -p 100,100,300,200

Its the same result as using python.
The preview image is cropped, but not streched.

For now i see no chance to display an unstreched image on the official 7 inch touchscreen.
Its crazy that the screen has a non squared pixel size ....

Perhaps in the future a ratio flag for the preview output of the camera would be nice.
I sthis the right place to post e feature request ?

All the best,
Lee

Odd. That should definitely change the aspect, not crop. I'll try and find some time to check this today.

[jamesh]

Hello pi cam fellows,

I also tested the terminal command:

raspistill -p 100,100,300,200

Its the same result as using python.
The preview image is cropped, but not streched.

For now i see no chance to display an unstreched image on the official 7 inch touchscreen.
Its crazy that the screen has a non squared pixel size ....

Perhaps in the future a ratio flag for the preview output of the camera would be nice.
I sthis the right place to post e feature request ?

All the best,
Lee

Odd. That should definitely change the aspect, not crop. I'll try and find some time to check this today.

Hmm, definitely cropping. I thought that used to change the aspect....will ask around.

[6by9]

Hmm, definitely cropping. I thought that used to change the aspect....will ask around.

It looks like it has always been wrong, as it is RaspiPreview setting things up incorrectly.

I was expecting to set

Code: Select all

index 7656c87..0d64408 100644
--- a/host_applications/linux/apps/raspicam/RaspiPreview.c
+++ b/host_applications/linux/apps/raspicam/RaspiPreview.c
@@ -105,12 +105,16 @@ MMAL_STATUS_T raspipreview_create(RASPIPREVIEW_PARAMETERS *state)
       preview_port = preview->input[0];
 
       MMAL_DISPLAYREGION_T param;
+      memset(&param, 0, sizeof(param));
       param.hdr.id = MMAL_PARAMETER_DISPLAYREGION;
       param.hdr.size = sizeof(MMAL_DISPLAYREGION_T);
 
       param.set = MMAL_DISPLAY_SET_LAYER;
       param.layer = PREVIEW_LAYER;
 
+      param.set |= MMAL_DISPLAY_SET_MODE;
+      param.mode = MMAL_DISPLAY_MODE_FILL;
+
       param.set |= MMAL_DISPLAY_SET_ALPHA;
       param.alpha = state->opacity;
 
@@ -121,11 +125,20 @@ MMAL_STATUS_T raspipreview_create(RASPIPREVIEW_PARAMETERS *state)
       }
       else
       {
+         param.set |= MMAL_DISPLAY_SET_NOASPECT;
+         param.noaspect = 1;
+
          param.set |= (MMAL_DISPLAY_SET_DEST_RECT | MMAL_DISPLAY_SET_FULLSCREEN);
          param.fullscreen = 0;
          param.dest_rect = state->previewWindow;
       }

and noaspect = 1 would mean that the aspect ratio is ignored and it gets stretched (as per docs at https://github.com/raspberrypi/userland ... deo.h#L189).

OK, found. In Raspistill the camera is set to output the same resolution as the size of the preview window - https://github.com/raspberrypi/userland ... spiStill.c. Raspivid behaves as I'd expect.
Really the camera preview ought to match the aspect ratio of the capture (something I've been meaning to fix for a while), but instead it's looking at the preview window size in several places.

[lee_w]

Hello,

Found a solution for python.

GingerAdams wrote an addition "** noaspect **"
you can find it here:
https://github.com/waveform80/picamera/ ... 3667fda1c9

simply replace the 3. files at /usr/lib/python3/dist-packages/

picamera/camera.py
picamera/mmal.py
picamera/renderers.py


then this code works for me:

import time

from picamera import PiCamera

camera = PiCamera()
camera.resolution = (1920,1080)

time.sleep(1)
camera.preview_fullscreen=False
camera.preview_window=(100, 100, 800, 100)
camera.start_preview(resolution=(800, 480), noaspect=True)
time.sleep(11111)


hopefully, this will get part of the main distro of picamera.

best,
lee