Why does my panorama stitch black images instead of actual images?

Question

I want to stitch some images(identical resolution) into a panorama using openCV(without using the Stitcher class). I tried the algorithm described here, but instead of the desired panorama i get an image that is made up of the last image to be stitched and a large black area. I outputted am image for each iteration and the result is the same: current image + a larger black area each time.

import numpy
import cv2

# images is an array of images that i need to stitch

matcher = cv2.DescriptorMatcher_create(cv2.DescriptorMatcher_BRUTEFORCE_HAMMING)
ORB = cv2.ORB_create()
homography = 0
panorama = 0

for image in range(0, len(images) -1):
    key1, desc1 = ORB.detectAndCompute(images[image], None)
    key2, desc2 = ORB.detectAndCompute(images[image + 1], None)

    matches = matcher.match(desc1, desc2, None)
    matches = sorted(matches, key=lambda x: x.distance, reverse=True)
    numGoodMatches = int(len(matches) * 0.15)
    matches2 = matches[-numGoodMatches:]

    points1 = numpy.zeros((len(matches2), 2), dtype=numpy.float32)
    points2 = numpy.zeros((len(matches2), 2), dtype=numpy.float32)

    for i, match in enumerate(matches2):
        points1[i, :] = key1[match.queryIdx].pt
        points2[i, :] = key2[match.trainIdx].pt

    h, mask = cv2.findHomography(points2, points1, cv2.RANSAC)

    if isinstance(homography, int):
        homography = h
        img1H, img1W = images[image].shape
        img2H, img2W = images[image + 1].shape
        aligned = cv2.warpPerspective(images[image + 1], h, (img1W + img2W, img2H))
        stitchedImage = numpy.copy(aligned)
        stitchedImage[0:img1H, 0:img2W] = images[image]
        panorama = stitchedImage
    else:
        h *= homography
        homography = h
        img1H, img1W = panorama.shape
        img2H, img2W = images[image + 1].shape
        aligned = cv2.warpPerspective(images[image + 1], h, (img1W + img2W, img2H))
        stitchedImage = numpy.copy(aligned)
        stitchedImage[0:img1H, 0:img2W] = images[image + 1]
        panorama = stitchedImage

Example of images i get:

The first image is correct.

The last image has the correct width (n * original width) but only one image and the rest is black area.

I've put an `imsave` for every iteration and got the images i posted(plus another 2 that were like the last one) and i could see that after each iteration, the image saved is the current image plus an extra black `width`(compared with the last oteration). But i cannot figure out why — beginner420, Jan 05 '21 at 14:50

score 0 · Answer 1 · answered Jan 05 '21 at 16:42

0

This

stitchedImage[0:img1H, 0:img2W] = images[image + 1]

places an image to the left top corner of "stitchedImage".

Somehow the image x offset must be calculated for each part of panorama:

stitchedImage[0:img1H, x_offset:x_offset+img2W] = images[image + 1]

answered Jan 05 '21 at 16:42

Hihikomori

950
6
12

Thanks for the tip. It still doesn't work, but im getting closer – beginner420 Jan 05 '21 at 20:46

Why does my panorama stitch black images instead of actual images?

1 Answers1