RGB to 32 Bit Gray

[Phase GmbH]

Hi Wayne,

I tried your Macro (IJ 1.35g, Windows XP). It worked however the resulting 32 bit gray image turned out to be inverted,a matter of byte order??

Christian Kreutzfeldt

[Wayne Rasband]

> I tried your Macro (IJ 1.35g, Windows XP). It worked however the
> resulting 32 bit gray image turned out to be inverted,a matter of byte
> order??

The newImage() function was creating an image with an inverting lookup
table. Adding 'black' (fill with black) to the second argument fixes
the problem. Here is the updated macro.

    if (bitDepth!=24)
        exit("RGB image required");
    setBatchMode(true);
    w = getWidth;
    h = getHeight;
    rgb = getImageID;
    newImage("32-bit", "32-bit black", w, h, 1);
    float = getImageID;
    for (y=0; y<h; y++) {
        showProgress(y, h);
        for (x=0; x<w; x++) {
            selectImage(rgb);
            v = getPixel(x,y)&0xffffff;
            selectImage(float);
            setPixel(x, y, v);
        }
    }
    resetMinAndMax;
    setBatchMode(false);
    //run("16-bit");

-wayne

[ij-Newsgroup]

Hi Wayne,

I got the latest beta version and your macro works fine.

However, even with the revised version, the lookup table seems to be
inverted. For densitometry applications I would like black to stick out
as a mountain in a surface plot and white to become the lowlands. How
can I make sure black is **always** a high point in a surface plot when
using this conversion macro?

Thanks heaps! ImageJ is a great software!
Art

Wayne Rasband wrote:

>> I tried your Macro (IJ 1.35g, Windows XP). It worked however the
>> resulting 32 bit gray image turned out to be inverted,a matter of byte
>> order??
>
>
> The newImage() function was creating an image with an inverting lookup
> table. Adding 'black' (fill with black) to the second argument fixes the
> problem. Here is the updated macro.
>
>    if (bitDepth!=24)
>        exit("RGB image required");
>    setBatchMode(true);
>    w = getWidth;
>    h = getHeight;
>    rgb = getImageID;
>    newImage("32-bit", "32-bit black", w, h, 1);
>    float = getImageID;
>    for (y=0; y<h; y++) {
>        showProgress(y, h);
>        for (x=0; x<w; x++) {
>            selectImage(rgb);
>            v = getPixel(x,y)&0xffffff;
>            selectImage(float);
>            setPixel(x, y, v);
>        }
>    }
>    resetMinAndMax;
>    setBatchMode(false);
>    //run("16-bit");
>
> -wayne

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