• Namespace (25/25) Apr 13 2013 I have a problem and maybe one you can explain, why this failure
• Namespace (2/2) Apr 13 2013 Forget to say: Of course I use the .ptr property to load the
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (10/28) Apr 13 2013 Make sure that you really do not need to multiply that byte count with
• bearophile (6/8) Apr 13 2013 Consider using something like:
• Namespace (11/19) Apr 13 2013 Nice idea. That works too.
• Namespace (17/17) Apr 14 2013 It seems that no content is copied with memcpy if I allocate with
• Namespace (1/1) Apr 14 2013 Maybe new allocate the original pixel memory? o.O
• Namespace (5/5) Apr 14 2013 Hehe... I found this in my getPixel method after the allocation

"Namespace" <rswhite4 googlemail.com> writes:

I have a problem and maybe one you can explain, why this failure 
happen.
Initial situation:
I have a opengl texture and I want to copy the pixel. I store the 
original pixel in an ubyte pointer and allocate new pixel memory 
with:
ubyte[] newPixel = new ubyte[this.width * this.height * 
this.depth];
and copy the pixel with
newPixel[] = *orgPixel;
or
memcpy(&newPixel[0], orgPixel, this.width * this.height * 
this.deph);

Both compiles without errors or warnings.
But if I want to store the newPixel in a new Texture, I see only 
black, no matter what method I use.
But if I change my allocation to
ubyte* newPixel = cast(ubyte*) GC.malloc(this.width * this.height 
* this.deph * ubyte.sizeof);
and copy then with
memcpy(&newPixel[0], orgPixel, this.width * this.height * 
this.deph);

it works fine and I see the copied texture.

My question is: why? What is the difference between both ways of 
allocations?

"Namespace" <rswhite4 googlemail.com> writes:

Forget to say: Of course I use the .ptr property to load the 
newPixel into the texture, if I use the ubyte storage.

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 04/13/2013 02:22 PM, Namespace wrote:

 I have a opengl texture and I want to copy the pixel. I store the
 original pixel in an ubyte pointer and allocate new pixel memory with:
 ubyte[] newPixel = new ubyte[this.width * this.height * this.depth];

Make sure that you really do not need to multiply that byte count with 
the .sizeof property of the actual value. But I guess it is fine because 
the elements are ubyte and ubyte.sizeof is 1.

 and copy the pixel with
 newPixel[] = *orgPixel;

That copies the first element of orgPixel to every element of newPixel. 
Probably not something that you want.

 or
 memcpy(&newPixel[0], orgPixel, this.width * this.height * this.deph);

That is different. Now you are copying all of the elements at orgPixel.

 Both compiles without errors or warnings.
 But if I want to store the newPixel in a new Texture, I see only black,
 no matter what method I use.

Are you sure that the memcpy method doesn't work?

 But if I change my allocation to
 ubyte* newPixel = cast(ubyte*) GC.malloc(this.width * this.height *
 this.deph * ubyte.sizeof);
 and copy then with
 memcpy(&newPixel[0], orgPixel, this.width * this.height * this.deph);

 it works fine and I see the copied texture.

 My question is: why? What is the difference between both ways of
 allocations?

Can you show two small programs that behaves differently. :)

Ali

"bearophile" <bearophileHUGS lycos.com> writes:

Namespace:
 I have a problem and maybe one you can explain, why this 
 failure happen.

Consider using something like:

auto newPixel = orgPixel[0 .. this.width * this.height * 
this.depth].dup;

Bye,
bearophile

"Namespace" <rswhite4 googlemail.com> writes:

On Saturday, 13 April 2013 at 22:18:21 UTC, bearophile wrote:
 Namespace:
 I have a problem and maybe one you can explain, why this 
 failure happen.

 Consider using something like:

 auto newPixel = orgPixel[0 .. this.width * this.height * 
 this.depth].dup;

 Bye,
 bearophile

Nice idea. That works too.
Here an overview:

ubyte* before = cast(ubyte*) this.getPixels();

size_t size = this.width * this.height * 4;
ubyte* after = cast(ubyte*) GC.malloc(ubyte.sizeof * size); /// 
works
//ubyte[] after = before[0 .. size].dup; /// works
//ubyte[] after = new ubyte[size]; /// doesn't work
memcpy(after/*.ptr*/, before, size);

It's a bit strange.

"Namespace" <rswhite4 googlemail.com> writes:

It seems that no content is copied with memcpy if I allocate with 
new.
The memory is nulled.
If I allocate with GC.malloc or with .dup I get the correct 
content.
That seems like a bug. And I cannot give you an simple example 
because my code works together with derelict etc. Would be too 
much work to create an simple example.

The mysterious thing is:
I store the pixel into a file. If I store the original pixel I 
get only the correct output, if I don't use the allocations of 
newPixel with new.
If I use
ubyte[] newPixel = new ubyte[size];
The original pixel memory is nulled. That is the explanation why 
memcpy seems not to work: memcpy works but the original pixel is 
nulled so nothing is copied. But that is weird...

"Namespace" <rswhite4 googlemail.com> writes:

Maybe new allocate the original pixel memory? o.O

"Namespace" <rswhite4 googlemail.com> writes:

Hehe... I found this in my getPixel method after the allocation 
of the pixel memory:
scope(exit) delete pixels;
Do not know what I was thinking.
My fault. :)