CODEWITHSUNDEEP
ffmpegrotation
SebSob
SebSob

Reputation: 582

FFmpeg filter to rotate image around point

Does anyone know how to rotate an image to its start point (top-left corner) instead of the center point (default) with the FFmpeg -vf rotate?

In this example I try to rotate a red squared image (test_sq.png) 30 degrees from its start point on in.png placed at coord 423:259 resulting in out.png.

This is my command:

ffmpeg -y -i in.png -pix_fmt bgra -strict experimental -vf movie=test_sq.png scale=279:279 rotate=30*PI/180:c=none:oh=ow [sticker]; [in][sticker] overlay=423:259 [out] -s 1280x720 out.png

To visualize it:

Results

As you can see it rotates from its center point and also clips the original image, not really good. Anyone have suggestions or ideas how to achieve what i need?

Upvotes: 3

Views: 4460

Answers (1)

Gyan
Gyan

Reputation: 93221

Your output width and height in the rotate filter are initialized to the input W/H and not auto-calculated to show the entire image after rotation. Use this instead,

ffmpeg -y -i in.png -i test_sq.png  \
-filter_complex "[1]scale=279:279,setsar=1,rotate=PI/6:c=none:ow=rotw(PI/6):oh=roth(PI/6)[s];
                 [0][s]overlay=423-w*sin(PI/6)/(sin(PI/6)+cos(PI/6)):259,scale=hd720[out]" \
-map "[out]"-pix_fmt bgra out.png

For a non-square image,

ffmpeg -y -i in.png -i test_sq.png  \
-filter_complex "[1]scale=279:279,setsar=1,rotate=PI/6:c=none:ow=rotw(PI/6):oh=roth(PI/6)[s];
                 [0][s]overlay=423-ih*sin(PI/6):259,scale=hd720[out]" \
-map "[out]"-pix_fmt bgra out.png

(You'll have to manually supply the value of ih (height of original image).

For a non-square image, with a negative rotation

ffmpeg -y -i in.png -i test_sq.png  \
-filter_complex "[1]scale=279:279,setsar=1,rotate=-PI/6:c=none:ow=rotw(-PI/6):oh=roth(-PI/6)[s];
                 [0][s]overlay=423:259-iw*sin(PI/6),scale=hd720[out]" \
-map "[out]"-pix_fmt bgra out.png

(You'll have to manually supply the value of iw (width of original image).

For images without in-built alpha, insert format=bgra before the rotate filter.

Upvotes: 7

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