How do I set output size of orthomosaic

[Samuel]

I have been developing some code to automatically process, save and export data. For part of the necessary use of the data I need the orthomosaic to be of a certain maximum dimension, using the gui I can just use the "Max. dimention (pix): " option to set the maximum size for the exported image.

My question is: How do I do that with python? the only options I have found in the API are dx, dy which the API makes sound to be the programmatic version of the gui's "Pixel size: "  option, or blockh, blockw which seem to relate to the "Split into blocks (pix):" option.

currently i am using some python code to resize the full sized orthomosaic down to what I need after exporting but every time it runs I get a "pixel count too large: could be a decompression bomb attack" warning.

PhotoScan Version: 1.3.2 build 4205 (64 bit)

[mikeb]

I'm also very interested in a solution regarding this problem.
I'm also running into the same problem. And I also need the function to export the orthomosaic in a specific dimension in pix.

Hope someone got an answer for this.

[Alexey Pasumansky]

Hello mikeb,

You can use the following methods related to orthomosaic to calculate the require export resolution:
chunk.orthomosaic.width
chunk.orthomosaic.height
chunk.orthomosaic.resolution

So if you need to export the orthomosaic using max-dimension = X, then I think you can use the following:

Code: [Select]

dx = dy = max(chunk.orthomosaic.width, chunk.orthomosaic.height) * chunk.orthomosaic.resolution / X

[mikeb]

Thank you for your answer, but it still export a huge image.
I want the maximum size of the orthomosaic the same size as my exported DEM.
In the GUI I choose in the export window Max. dimension (pix) and choose 4122.
But if I do it in the python script the size is still the same. I think its not possible to use dx and dy the same so I just use one of it and still does not work. If I use dx and dy in the exportorthomosaic function it returns with an Runtime Error: Empty Raster.
Can you tell what I'm doing wrong. I want to use the same size as my DEM (max dimension = 4122)

Here is my codesnippet:

Code: [Select]

dx = dy = max(chunk.orthomosaic.width, chunk.orthomosaic.height) * chunk.orthomosaic.resolution / 4122.0

chunk.exportOrthomosaic(project_path + project_name + ".tif", image_format=PhotoScan.ImageFormatTIFF, format = PhotoScan.RasterFormatTiles, dy=dy, raster_transform=PhotoScan.RasterTransformNone, write_kml=False, write_world=True)


[Alexey Pasumansky]

Hello mikeb,

Is your project referenced in WGS84?

If so, then you need to convert meters for dx and dy parameters to degrees.

[Alexey Pasumansky]

Hello mikeb,

Here's a small code for conversion from meters to lat/long values. As source export resolution it takes the DEM resolution:

Code: [Select]

import PhotoScan, math

dx = dy = chunk.elevation.resolution


coord = PhotoScan.Vector([0,0,0])
cam_num = 0
for camera in chunk.cameras:
if not camera.transform:
continue
coord += chunk.crs.project(chunk.transform.matrix.mulp(camera.center))
cam_num += 1

crd = (1. / cam_num) * coord

#crd = chunk.crs.project(chunk.transform.matrix.mulp(chunk.region.center))

v1 = crd.copy()
v2 = PhotoScan.Vector([crd.x + 0.001, crd.y, crd.z])
vm1 = chunk.crs.unproject(v1)
vm2 = chunk.crs.unproject(v2)
res_x = (vm2 - vm1).norm() * 1000

#latitude
v2 = PhotoScan.Vector([crd.x, crd.y + 0.001, crd.z])
vm2 = chunk.crs.unproject(v2)
res_y = (vm2 - vm1).norm() * 1000

dx = dx / res_x
dy = dy / res_y

path = project_path + project_name + ".tif"
chunk.exportOrthomosaic(path, image_format=PhotoScan.ImageFormatTIFF, format = PhotoScan.RasterFormatTiles, dx=dx, dy=dy, raster_transform=PhotoScan.RasterTransformNone, write_kml=False, write_world=True)