I have an image element of the SVG inb the HTML5,
The image size is:
(stretch, preserveAspectRatio is set to "none")
width=520px
height=240px
then, I modify it to maintain aspect ratio (preserveAspectRatio is set to defer)
because width>height,
the height still the same = 240px
but how can I calculate the new width (it is shrinked because the maintain aspect ratio)
is there a formula to this?
viewBox width / viewBox height * 240px I imagine.
Related
when I set the width and height of canvas in pixels, its works fine but when I set the width and height like '10cm' or something, it doesn't works. What am I doing wrong? can we only set the canvas in pixels? not in any other? I am working on SVG and convert it to canvas to save as image file, my SVG canvas's width and height is in cm so I want that canvas should be in cm too, otherwise the final image crops the data of SVG.
I have a four element position vector [xmin ymin width hight] that specifies the size and position of crop rectangle from image I. How can i find the new position and size for the resized image I?
It is not entirely clear, what you want, as we don't know your coordinate system. Assuming x is the horizontal axis and y is the vertical axis and your point (1,1) is at the top left corner, you can use the following snippet:
p = [xmin ymin width height];
I = I_orig(p(2):p(2)+p(4)-1,p(1):p(1)+p(3)-1);
The size is of course your specified width and height.
You can convert your original bounding box to relative values (that is assuming the image size is 1x1)
[origH origW] = size( origI(:,:,1) );
relativeBB = [xmin / origW, ymin / origH, width / origW, hight / origH];
Now, no matter how you resized your origI, you can recover the bounding box w.r.t the new size from the relative representation:
[currH currW] = size(I(:,:,1));
currBB = relativeBB .* [currW, currH, currW, currH];
You might need to round things a bit: you might find floor better for xmin and ymin and ceil more suitable for width and height.
This is a general question regarding an algorithm to zoom an image to fit the width of a screen, there are some givens and some constraints. We can assume we are using Java but this question is more mathematical that language dependent.
First of all, the image loads and fits into the dimensions of the screen vertically first, not horizontally.
We can get the dimensions of the screen and the dimensions of the image with methods, but we cannot set the dimensions of either (We only have getters not setters).
imageWidth = image.getWidth(); //integer
imageHeight = image.getHeight(); //integer
screenWidth = screen.getWidth(); //integer
screenHeight = screen.getHeight(); //integer
The only method to resize the image is by setting scale (zooming essentially).
image.setScale(some float); // optionally image.setZoom(integer);
What I would like to know is how to calculate the scale (zoom) level for some l x h image so that it fits a L x H screen horizontally?
All you have to do to make the Image fill your screen is scale along the x axis:
scaling_factor = screen.getWidth()/image.getWidth()
image.setScale(zoom_factor);
The formula is very intuitive:
The image height is irrelevant. The scaling you desire would be the same for a landscape and vertical image, as long as the width of both images are the same
When the image's width increases, your scaling factor decreases
When your screen size increses, the scaling factor increases.
I need to generate new dimensions for an image to match a ratio of a given width and height ...but without increasing the size of the original.
The concept seems oh so simple yet I can't seem to join the dots.
Also, for code samples the language is PHP.
Update:
This is what I have so far:
http://codepad.org/fTdCNhQf
This is the output I need:
Example Image • (can't embed yet)
Since enlarging is not an option, your only options are cropping and extending.
Try this: let's say your image is W*H, and the desired aspect ratio of width to height is R.
Using the width and the aspect ratio, calculate the target height TH = W/R
Using the height and the aspect ratio, calculate the target width TW = H*R
Calculate area changes aH = ABS(TH-H)*W and aW = ABS(TW-W)*H
if aH is less than aW, use target width; pad or crop the image horizontally based on the sign of TH-H
Otherwise, use target height; pad or crop the image vertically based on the sigh of TW-W
Here is a quick example:
Target R: 5/6
Image: W=200, H= 300;
TH = 200/5*6 = 240
TW = 300*5/6 = 250
aH = 60*200=12000
aW = 50*300=15000
Resulting action: since aH is less than aW, crop image vertically to 240
Are you using something like ImageMagick libraries to generate an image or do you just need to generate the new dimensions based on a known ratio? Also, do you need to discover the ratio from the existing image?
This may be useful then:
http://www.zedwood.com/article/119/php-resize-an-image-with-gd
I need an algorithm that given an image's width, height and a target ratio will calculate the number of pixels to be shaved from the image's sides to get to that ratio, that has the smallest change in the image's area.
How might one implement such an algorithm?
Edit
Sorry for the inconsistency in my original question; I have revised my it.
Bring the ratio into reduced form, so that gcd(ratio_width, ratio_height) = 1.
Calculate floor(width / ratio_width) and floor(height / ratio_height). Your factor is the minimum of these two.
Multiply ratio_width and ratio_height by that factor to obtain the new image dimensions.
Shave the difference.
To minimize the change in area, you want to find the largest rectangle of the desired aspect ratio that will fit inside the original image bounds.
So, if the original image is too wide, then make the final image's height = original height, and shave off the extra width.
If the original image is too tall, make the final image's width = original width, and shave off the extra height.
Note: This assumes that you are not allowed to increase the width or height beyond the original dimensions. If that is not the case, the algorithm would be:
Constraint 1: x_final * y_final = x_initial * y_initial
Contraint 2: x_final / y_final = r
The solution is:
x_final = sqrt(r*x_initial*y_initial)
y_final = sqrt(x_initial*y_initial/r)