Bitmap Transforms

[warren]

I am trying to manipulate the bitmap transform matrix in other ways than rotate and scale. 

www.simos.de/bilder/Datenbl%C3%A4tter-AN/AN1.pdf, p96
www.ftdichip.com/Support/Documents/AppNotes/AN_314_FT800_Advanced%20Techniques_Working%20with%20Bitmaps.pdf, p14

It looks like it can be done, but I don't know how to change these from the arduino's environment.

Thanks,
Warren Davis

[jamesbowman]

You can scale, rotate and translate bitmaps using the commands listed on p. 42-45 of the book.

These commands are actually just setting the bitmap matrix - this is what controls the bitmap transform. You can directly set this matrix using low-level commands like this:


GD.BitmapTransformA(256);
GD.BitmapTransformB(0);
GD.BitmapTransformC(0);
GD.BitmapTransformD(0);
GD.BitmapTransformE(256);
GD.BitmapTransformF(0);


The six-element matrix works as a transform like this:


A     B     C
D     E     F


and the hardware divides each element by 256, so the above code actually sets the matrix to the identify:


1.0    0    0
 0  1.0    0


So to make a matrix to shrink every bitmap by half:


GD.BitmapTransformA(512);
GD.BitmapTransformB(0);
GD.BitmapTransformC(0);
GD.BitmapTransformD(0);
GD.BitmapTransformE(512);
GD.BitmapTransformF(0);


[jk]

I have an question related to this post. I want to zoom a bitmap with x,y pixel to the double size 2x,2y, as shown on page 45. What are the neccesary commands to make the whole bitmap visible?
Before doing this I would like to calculate the width and height after loading the jpeg (with getprops command?).
Could you help with a code snippet for this.

[jamesbowman]

Sure, if you have a bitmap sized (x, y) and want to zoom it to double size, then you do two things: increase its on-screen size, and load a "2x" transform.

To increase its on-screen size:

GD.BitmapSize(NEAREST, BORDER, BORDER, 2 * x, 2 * y);

and to load the "2x" transform:

GD.cmd_scale(F16(2), F16(2));
GD.cmd_setmatrix();
After this, drawing the bitmap will result in the double-sized version.

[jamesbowman]

Sure, if you have a bitmap sized (x, y) and want to zoom it to double size, then you do two things: increase its on-screen size, and load a "2x" transform.

To increase its on-screen size:

GD.BitmapSize(NEAREST, BORDER, BORDER, 2 * x, 2 * y);

and to load the "2x" transform:

GD.cmd_scale(F16(2), F16(2));
GD.cmd_setmatrix();
After this, drawing the bitmap will result in the double-sized version.

[Ulrich]

In my example this code snippet doesn't work. The bitmap Pixel are Doubled but the viewport is always the the original one so that only the left upper Region of the doubled bitmap is shown.

What's wrong?

[Ulrich]

Feb 27, 2016 0:41:28 GMT -8 Ulrich said:

In my example this code snippet doesn't work. The bitmap Pixel are Doubled but the viewport is always the the original one so that only the left upper Region of the doubled bitmap is shown.

What's wrong?

To be more accurate: when I load more jpegs (with handle numbers 0, 1, 2, ...) only the first one (with handle 0) is displayed correctly. For the bitmaps 1, 2, 3, ... only the left upper quadtrant is shown.



Best Regards

Ulrich