如何让图像沿着路径缩小，但不变形，且可以偏移？

I'm not entirely sure I understand what you want, but here are some steps with visuals that I hope might bridge the language barrier.

If you want to make a brush that will maintain the proportions of the triangle, have the width of the stroke get smaller, and not show the portion of the triangle on the other side of the stroke, we'll make a shape, a blend, an art brush, and two copies of the spiral.

Shape

1. Make the triangle. Make a horizontal line. Align their centers. Give the path no stroke. Use the Shapebuilder Tool to separate the lower section of the triangle, but don't delete it. Fill the lower portion of the triangle with no fill and no stroke.

(Image zoomed in to show detail)

Blend

Duplicate the triangle shape, scale down one of the triangles, and make a blend. Adjust spacing and scale as needed.

Brush

I'm recommending a brush instead of a blend because when I tried to replace the spline, the orientation of the triangles wasn't what I think you wanted. So take the entire blend and make an art brush.

Spiral

Make your spiral with the Spiral Tool and make a copy of it. On the first spiral, apply the brush.

On the second copy, use Width Profile 4 in the Variable Widths Profiles and set the stroke big enough to see the change in size.

Now align the vertical and horizontal centers of the 2 spirals.

I hope that helps.

crep,

If you look closely, you can see the bending of the triangles at the inner end of the spiral.

You can get a better appearance with a more even distribution of triangles, with a combination of:

A) A Blend from a small triangle to a large triangle with identical proportions and a ratio of sizes equalling that of the (desired) Stroke Weight at the ends, see B), setting Orientation to Align to Path and setting Spacing to Specified Distance with the desired distance;

B) Either a stroked path with a Width Profile or basic path and an Art Brush with the desired width change between the ends corresponding to the desired variation in (apparent) Stroke Weight applied to a basic path with a Stroke Weight of 1pt, and in addition a copy path for the Blend from A);

where you apply the Blend from A) to the copy path from B), then form a Group.

Edit: At my second read, as I (mis)understand it, you wish to have the triangles point into (the centre of) the path from the outside.

You can obtain that by mirroring each triangle vertically so that you have one triangle pointing down and a nostroke/nofill copy triangle pointing up, the two meeting at their coinciding points/tips, then align the two sets (large triangles and small triangles) horizontally.

With this, the lower triangles (forming the lower half of the Blend) will be invisible under the spiral path and the the upper ones will be visible over (and into) the path.

If the Blend goes the wrong (opposite) way, you may click either the inner or outer end of the copy path with the Pen Tool (and the same for the original path if the Width/Art Brush is wrong).

EVen when translating this via Google Translator I don't understand where the problem is. What's happening there is to be expected with this brush.