[reportlab-users] Loading transparent GIFs with shapes.Image

[Marcel Tromp]

Target is pdf. However, I have not been using canvas in my scripts. So far I
have been grouping shapes (including images) in groups, which ultimately get
added to a Drawing, which get rendered to a pdf.

In this method, transparency does not work.

What is the benefit to use canvas instead beyond the image rendering?

MT
--



On Thu, Nov 12, 2009 at 4:58 AM, Robin Becker <robin at reportlab.com> wrote:


> Marcel Tromp wrote:

>

>> Anyone? Is there anyway to have overlapping bitmap images that use

>> transparency to show the lower/earlier image?

>>

>>  I don't believe that shapes.Image supports any notion of transparency. Al

> of the reportlab graphs renderers depend explicitly on properties of the

> different back ends so it's fairly hard to support some of the more advanced

> concepts like overPrint and transparency.

>

> You don't say which back end is being used. If you want to put images onto

> a PDF document then the pdfgen canvas already supports bitmaps with RGBA and

> a transparent colour.

>

> If you're talking about the PM renderer then that's not done. The code is

> in renderPM.py

>

>>        def drawImage(self, image):

>>                if image.path and os.path.exists(image.path):

>>                        if type(image.path) is type(''):

>>                                im =

>> _getImage().open(image.path).convert('RGB')

>>                        else:

>>                                im = image.path.convert('RGB')

>>                        srcW, srcH = im.size

>>                        dstW, dstH = image.width, image.height

>>                        if dstW is None: dstW = srcW

>>                        if dstH is None: dstH = srcH

>>                        self._canvas._aapixbuf(

>>                                        image.x, image.y, dstW, dstH,

>>                                        im.tostring(), srcW, srcH, 3,

>>                                        )

>>

>

>

> so we would need to modify this.

>

> Effectively im is a PIL image and we mash it directly onto our internal RGB

> buffer using libart's function art_rgb_pixbuf_affine.

>

> Libart does have a function art_rgb_rgba_affine which could be used to mash

> an RGBA style image onto the RGB canvas. That would allow RGB + transparent

> colour or RGBA style sources to be used for the incoming image. Of course

> then we'd need to start looking at the Image processing for the other

> graphics renderers.

> --

> Robin Becker

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