绕 x 轴旋转图像

Question

我需要绕其 x 轴（或 y 轴）旋转图像。我可以使用 avisynth 轻松创建这样的动画，但现在我需要使用 Python 的 moviepy 模块来实现该效果。我可以使用以下脚本轻松旋转图像，但需要一些线索如何以 2D 或 3D 旋转图像。

from moviepy.editor import *

clip = ImageClip('my_image.jpg')
rotated_clip = (clip.add_mask()
                .fx(vfx.resize, width=300, height=300)
                .fx(vfx.rotate, lambda t: 90*t, expand=False)
                .set_duration(5))
final_clip = CompositeVideoClip([rotated_clip.set_pos("center")], size=(800,800), bg_color=3*[255])
final_clip.write_videofile("test.mp4", fps=25, codec="libx264")

这是实际生成该示例图像的 avisynth 脚本。请注意，它确实需要“QUAD”插件。

function stars(clip c, int r) {
    c.Overlay(x=rand(c.width),y=rand(c.height),BlankClip(c,width=1,height=1,color=$030301*rand(85)))
    (r==0)? last : stars(r-1)
    Trim(0,-1).Loop(c.Framecount, 0, 0)
}
width= 800
height=600
length=100000
Tcolor=$000040
Bcolor=$000018

StackVertical(BlankClip(length=length,width=2,height=1,color=TColor,pixel_type="RGB32"),BlankClip(length=length,width=2,height=1,color=BColor)).BilinearResize(width,2*height,src_top=0,src_height=2).Crop(0,height/2,0,-height/2).Stars(width*height/3072)

ImageSource("path_to_image.png", start=0, end=total_time, fps=300, pixel_type="RGB32")
#BlankClip(length=length,FPS=25,width=640,height=480,color=$000018,pixel_type="RGB32")

#ColorBars()
HALFCYCLE=10                        # Frames in 1 HALF rotation (spinning clip)
NSPIN   = 1                         # Number of HALF rotations in spinning clip
NSTILL  = 10                        # Frames in STILL clip
V       = 0.2                       # Tilt/Yaw
tim     = PI / HALFCYCLE

ScriptClip("""

    c=last
    t=tim*current_frame
    t1x= 0.5 -  0.5 * cos(t)        # BOTH Left
    t2x= 0.5 +  0.5 * cos(t)        # BOTH Right
    #
    t1y= 0.0 +  V * sin(t)          # ] both Top's opposite sign
    t2y= 0.0 -  V * sin(t)          # ] 
    t3y= 1.0 +  V * sin(t)          # [ both Bottoms opposite sign
    t4y= 1.0 -  V * sin(t)          # [
    ResetMask
    quad(t1x,t1y, t2x,t2y, t2x,t3y, t1x,t4y,  normal=true)
    #Overlay(c,last,mask=last.ShowAlpha())


""")

SPIN=Trim(0,-(NSPIN*HALFCYCLE +1))     # Spinning clip, + 1 to complete last spin
STILL=SPIN.Trim(SPIN.FrameCount-1,-1).Loop(NSTILL,0,0)
SPIN2=Trim((NSPIN%2 ==0)?0:HALFCYCLE,-(NSPIN*HALFCYCLE +1))
SPIN ++ STILL ++ SPIN2
Return Last

Answer 1

实现此目的的一种方法是使用Vapory，这是MoviePy作者的另一个库，它方便了通过Python操作POV-Ray。您可以在 3D 场景中创建一个矩形，然后围绕您喜欢的任何轴旋转它，以一定的间隔将帧保存到 MoviePy 剪辑中。

MoviePy + Vapory 代码

from moviepy.editor import concatenate, ImageClip, VideoClip
from vapory import *  # Yes, this is the library author's suggested usage.

img_path = './baseball.png'
img_clip = ImageClip(img_path)
W, H = img_clip.w, img_clip.h # Image width and height
AR = 1.0*W/H  # Aspect ratio used when scaling later

t_rev   = 2.0       # Time (in seconds) to complete one full revolution
t_half  = t_rev*0.5 # Time required for a half revolution
t_still = 0.8       # Time to hold the half rotated image still
frame_rate = 15 # Number of frames per second in the output

# Static POV-Ray objects
cam = Camera('location', [ 0,  0, -1],
             'look_at',  [ 0,  0,  0])
light = LightSource([0, 0, -1]) # Light at camera location
bg = Background('color', [0, 0, 0]) # Black background

def scene(t):
    """Returns the scene at time t (in seconds)."""
    s = Scene(camera = cam, objects = [light, bg])

    # Add POV-Ray box with image textured on it
    s = s.add_objects([
        Box(
            [0, 0, 0],
            [W, H, 0],
            Texture(
                Pigment(ImageMap('"{}"'.format(img_path), 'once')),
                Finish('ambient', 1.0)
            ),
            'translate', [-0.5, -0.5, 0], # Center box in field of view
            'scale', [AR, 1, 0], # Scale to given aspect ratio
            'rotate', [0, (360/t_rev)*t, 0], # Can change rotation axis here
        ),
    ])
    return s

def make_frame(t):
    return scene(t).render(width=W, height=H, antialiasing=0.1)
 
still_1 = VideoClip(make_frame).to_ImageClip(t=0).set_duration(t_still)
half_1  = VideoClip(make_frame).subclip(0, t_half)
still_2 = VideoClip(make_frame).to_ImageClip(t=t_half).set_duration(t_still)
half_2  = VideoClip(make_frame).subclip(t_half, t_rev)

final_clip = concatenate([still_1, half_1, still_2, half_2])
final_clip.write_videofile("./baseball_rot.mp4", fps=frame_rate, codec="libx264")
# Or: final_clip.write_gif("./baseball_rot.gif", fps=frame_rate)

输出GIF

其他想法

要调整的主要变量是

img_path

、

t_rev

（完整 360 度旋转的时间）、

t_still

和

frame_rate

。 为了使视频编码正常工作，您可能需要裁剪和/或缩放，以便宽度和高度是 8 像素的倍数（GIF 输出不需要）。

使用光线追踪器来解决这个问题有点过分了，但这是我使用的第一种方法。 我想将图像表示为 3D 场景中的 2D 矩形，在其中我可以简单地指定旋转角度，3D 库将处理其余的事情。 使用 scikit-image 的投影变换应该可以解决这个问题，如此 MoviePy 示例所示。 请特别注意，该代码清单中间附近的

trapzWarp

函数。