Ok, so I rotated an image by 25 degrees like this :
MyImage.layer.affineTransform = CGAffineTransformMakeRotation(25);
Now I want to rotate the image again by 25 more degrees (50 degrees in total)
So my question is, How do I rotate X more degrees an image ?
If you have any other way to rotate an image or better way please include your code.
There is no need to know the current angle! Instead of setting the affineTransform, which is only a shortcut, apply an actual 3D transform. Now you can call CATransform3DRotate, which rotates an existing transform — and thus is additive.
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I am developing a GPS waypoint application. I have started by drawing my compass but am finding it difficult to implement degree text around the circle. Can anyone help me with a solution? The compass image am working on] 1 here shows the circle of the compass I have drawn.
This image here shows what I want to achieve, that is implementing degree text round the compass [Image of what I want to achieve] 2
Assuming you're doing this in a custom view, you need to use one of the drawText methods on the Canvas passed in to onDraw.
You'll have to do a little trigonometry to get the x, y position of the text - basically if there's a circle with radius r you're placing the text origins on (i.e. how far out from the centre they are), and you're placing one at angle θ:
x = r * cosθ
y = r * sinθ
The sin and cos functions take a value in radians, so you'll have to convert that if you're using degrees:
val radians = (degrees.toDouble() / 360.0) * (2.0 * Math.PI)
and 0 degrees is at 3 o'clock on the circle, not 12, so you'll have to subtract 90 degrees from your usual compass positions (e.g. 90 degrees on the compass is 0 degrees in the local coordinates). The negative values you get are fine, -90 is the same as 270. If you're trying to replicate the image you posted (where the numbers and everything else are rotating while the needle stays at the top) you'll have to apply an angle offset anyway!
These x and y values are distance from the centre of the circle, which probably needs to be the centre of your view (which you've probably already calculated to draw your circle). You'll also need to account for the extra space you need to draw those labels, scaling everything so it all fits in the View
I've got a bunch of thumbnails/icons packed right up next to each other in a texture map / sprite sheet. From a pixel to pixel relationship, these are being scaled up from being 145 pixels square to 238 screen pixels square. I was expecting to get +-1 or 2 pixel accuracy on the edges of the box when accessing the texture coordinates, so I'm also drawing a 4 pixel outline overtop of the thumbnail to hide this probable artifact. But I'm seeing huge variations in accuracy. Sometimes it's off in one direction, sometimes the other.
I've checked over the math and I can't figure out what's happening.
The the thumbnail is being scaled up about 1.64 times. So a single pixel off in the source texture coordinate could result in around 2 pixels off on the screen. The 4 pixel white frame over top is being drawn at a 1-1 pixel to fragment relationship and is supposed to cover about 2 pixels on either side of the edge of the box. That part is working. Here I've turned off the border to show how far off the texture coordinates are....
I can tweak the numbers manually to make it go away. But I have to shrink the texture coordinate width/height by several source pixels and in some cases add (or subtract) 5 or 6 pixels to the starting point. I really just want the math to work out or to figure out what I'm doing wrong here. This sort of stuff drives me nuts!
A bunch of crap to know.
The shader is doing the texture coordinate offsetting in the vertex shader...
v_fragmentTexCoord0 = vec2((a_vertexTexCoord0.x * u_texScale) + u_texOffset.s, (a_vertexTexCoord0.y * u_texScale) + u_texOffset.t);
gl_Position = u_modelViewProjectionMatrix * vec4(a_vertexPosition,1.0);
This object is a box which is a triangle strip with 2 tris.
Not that it should matter, but matrix applied to the model isn't doing any scaling. The box is to screen scale. The scaling is happening only in the texture coordinates that are being supplied.
The texture coordinates of the object as seen above are 0.00 - 0.07, then in the shader have an addition of an offset amount which is different per thumbnail. .07 out of 2048 is like 143. Originally I had it at .0708 which should be closer to 145 it was worse and showed more like 148 pixels from the texture. To get it to only show 145 source pixels I have to make it .0.06835 which is 140 pixels.
I've tried doing the math in a calculator and typing in the numbers directly. I've also tried doing like =1305/2048. These are going in to GLfloats not doubles.
This texture map image is PNG and is loaded with these settings:
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );
but I've also tried GL_LINEAR with no apparent difference.
I'm not having any accuracy problems on other textures (in the same texture map) where I'm not doing the texture scaling.
It doesn't get farther off as the coords get higher. In the image above the NEG MAP thumb is right next to the HEAT MAP thumb and are off in different directions but correct at the seam.
here's the offset data for those two..
filterTypes[FT_gradientMap20].thumbTexOffsetS = 0.63720703125;
filterTypes[FT_gradientMap20].thumbTexOffsetT = 0.1416015625;
filterTypes[FT_gradientMap21].thumbTexOffsetS = 0.7080078125;
filterTypes[FT_gradientMap21].thumbTexOffsetT = 0.1416015625;
==== UPDATE ====
A couple of things off the bat I realized I was doing wrong and are discussed over here: OpenGL Texture Coordinates in Pixel Space
The width of a single thumbnail is 145. But that would be 0-144, with 145 starting the next one. I was using a width of 145 so that's going to be 1 pixel too big. Using the above center of pixel type math, we should actually go from the center of 0 to the center of 144. 144.5 - 0.5 = 144.
Using his formula of (2i + 1)/(2N) I made new offset amounts for each of the starting points and used the 144/2048 as the width. That made things better but still off in some areas. And again still off in one direction sometimes and the other other times. Although consistent for each x or y position.
Using a width of 143 proves better results. But I can fix them all by just adjusting the numbers manually to work. I want to have the math to make it work out right.
... or.. maybe it has something to do with min/mag filtering - although I read up on that and what I'm doing seems right for this case.
After a lot of experiments and having to create a grid-lined guide texture so I could see exactly how far off each texture was... I finally got it!
It's pretty simple actually.
uniform mat4 u_modelViewProjectionMatrix;
uniform mediump vec2 u_texOffset;
uniform mediump float u_texScale;
attribute vec3 a_vertexPosition;
attribute mediump vec2 a_vertexTexCoord0;
The precision of the texture coordinates. By specifying mediump it just fixed itself. I suspect this also would help solve the problem I was having in this question:
Why is a texture coordinate of 1.0 getting beyond the edge of the texture?
Once I did that, I had to go back to my original 145 width (which still seems wrong but oh well). And for what it's worth I ended up then going back to all my original math on all the texture coordinates. The "center of pixel" method was showing more of the neighboring pixels than the straight /2048 did.
Say, I have an image on an HTML page.
I apply an affine transformation to the image using CSS3 matrix function.
It looks like:
img#myimage {
transform: matrix(a, b, c, d, tx, ty);
/* use -webkit-transform, -moz-transform etc. */
}
The origin of an HTML page is the top-left corner and the y-axis is inverted.
I'm trying to put the same image in an environment (cocos2d) where the origin is the bottom-left corner and the y-axis is upright.
To get the same result in the other environment, I need to transform the origin somehow and reflect that in the resulting CGAffineTransform.
It would be great if I can get some help with the matrix math that goes here. (I'm not so good with matrices.)
The following formula would work,
for converting the position from CSS3 to Cocos2d:
(screen Size - "y" position in CSS3 - height of object)
Explanation:
To make the origin for the Cocos environment same as for the CSS3 environment we would only have to add the screen size to the cocos2d's bodies y co-ordinate.
Eg. The screen size is (100,100) and the body is a point object if you place it at (0,0) in CSS3 it would be at the top left corner. If we add the screen size to the y co-ordinates for cocos2d the object would be placed at (0,100) which is the top-left corner for cocos2d as well
To make the co-ordinates same, since the Y axis is inverted, we have to subtract the "Y" co-ordinate given in CSS3 from the Screen Size for Cocos2d. Suppose we place the same point object in the previous example at (0,10) in CSS3 we would place it at (0, 100 - 10) in cocos2d which would be the same positions on the screen
Since our body would NOT always be a point object we have to take care of its anchor point as well. If suppose the body's height is 20 and we place it at (0,10) in CSS3 then it would be placed at the top-left position and would be coming down because the Y axis is inverted
Hence we would also have to subtract the body's total height from the screen size and "y" co-ordinate to place it at the same position which would be (0, 100 - 10 - 20) putting the body at the same place in cocos2d environment
I hope I am correct and clear :)
I want to flip image view on axis which is 45 degree left or right from Y axis. How can I obtain this new axis of rotation and how can I apply it to image view. Here is the link
of what I want to achieve.
https://www.youtube.com/watch?v=hDlp-aWq-uM&feature=youtu.be
Thanks!
Use Camera to achieve 3D rotation like View.setRotationY.
camera.save();
camera.rotateY(rotate);
camera.getMatrix(matrix);
matrix.preTranslate(-left, 0);
matrix.postTranslate(left, 0);
camera.restore();
canvas.save();
canvas.concat(matrix);
canvas.drawBitmap(...);
canvas.restore();
The result for my personal project can be viewed below.
You can achieve this with Matrix class
Matrix mtrx=new Matrix();
imageView.setScaleType(ScaleType.MATRIX);
mtrx.postRotate((float) angle, pivX, pivY);
imageView.setImageMatrix(mtrx);
you should override draw method or create your own image view class by extending ImageView, then to rotate the axis rotate the canvas in draw(), and for the flipping you can user objectanimator which is available for API 11+, and for pre-11 you can user nineoldandroids.com library located at below url
http://nineoldandroids.com/
Let's say I have point which has the coordinates (50,100) where (0,0) is in the upper left corner of a view.
How can I get the coordinates of the same point if I want the beginning of the coordinate system to be the center of the screen (ie width/2, height/2) ?
Note that I am implementing a custom View and I am drawing inside it and I just want to convert the coordinate inside that same view. I am basically implementing a graphic calculator and I need to have my coordinate system to start in the middle of the screen so the graphics could look better.
I notice you tagged it as iOS problem, so use the method Apple have built in UIView:
(CGPoint)convertPoint:(CGPoint)point fromView:(UIView *)view
Find the midpoint you will be using, so for a 100x100 screen, this would be (50,50). Then take the point you need to convert and subtract the midpoint X value from the point X value, and then subtract the point Y value from the midpoint Y value. Notice that you are not doing the same operation on both values.
So if the point is (30,25) the new point would be (-20,25) because 30 - 50 = -20 and 50 - 25 = 25.