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Newbie question. I just created a pyramid tif as a preprocessing step by running:
Now I have a tif with 7 "pages", where each page is half the resolution of the previous one. I want to allow users to request first |
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Replies: 2 comments 2 replies
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Hi @dersmon, That's the old vips7 interface. For vips8, use: As well as being easier to read, performance should be a little better too. By default libvips will use the full resolution image. You can select lower res levels with To crop from the 1/4 size level. |
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Thanks! So for the pipeline I would need to check first which page the requested resize would match best, then use that page to extract and do a final resize. |
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Ah I see. $crop_left = 100; // pixel coordinates in the full size image
$resize = 0.2; // the factor by which to scale the dimensions
// this is always quick and just gets the image metadata
$image = Vips\Image::newFromFile($filename)
$width = $image->width;
$target_width = $width * $resize;
// resize and then crop
$resize = Vips\Image::thumbnail($filename, $target_width);
$result = $resize->crop($crop_left * $resize,
$crop_top * $resize,
$crop_width * $resize,
$crop_height * $resize); |
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... libvips is demand-driven, so that will only resize the bit of the image you want, not the whole thing. |
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Hi @dersmon,
That's the old vips7 interface. For vips8, use:
As well as being easier to read, performance should be a little better too.
By default libvips will use the full resolution image. You can select lower res levels with
page, so perhaps:To crop from the 1/4 size level.