Rendering with matrix: missing features

[geisserml]

I would like to switch my rendering code from `FPDF_RenderPageBitmap()` to `FPDF_RenderPageBitmapWithMatrix()` because it is more feature-rich in terms of transformations (e. g. mirrored rendering, skew, rotating by an angle that is not a multiple of 90°, concatenated transformations, ...).

However, some functionality seems to be unavailable with matrix rendering:
* Form fields: It looks like it is not possible to render form fields with a custom transform matrix. I can only find `FPDF_FFLDraw()` but no matrix equivalent.
* Colour scheme: I can't find a function that can render with both custom colour scheme and matrix.

(* Progressive rendering: I can't find a function that can render both progressively and with matrix.)

In pypdfium2's rendering helper method, I'm publicly exposing the parameters `colour_scheme` and `draw_forms` already and would like to preserve this functionality, but still switch to matrix rendering.

Would it be possible to add methods like `FPDF_FFLDrawWithMatrix()` and `FPDF_RenderPageBitmapWithMatrixAndColorScheme()` to be able to profit from the full functionality, or is there some internal reason why these features can't be combined?

[geisserml]

> Would it be possible to add methods like `FPDF_FFLDrawWithMatrix()` and `FPDF_RenderPageBitmapWithMatrixAndColorScheme()` to be able to profit from the full functionality, or is there some internal reason why these features can't be combined?

Alternatively, perhaps some `FPDF_RenderPageBitmapWithConfig()` function taking a rendering configuration interface might be better? To avoid the necessity of adding a new function each time a new rendering parameter is introduced.

[Danis]

I've been using the code in the  attached patch in my local PDFium build.

The patch is against rev 5200 or so.

YMMV.

[geisserml]

Thanks, I'll check out the patch. Have you considered submitting this on https://pdfium-review.googlesource.com/ ?

[geisserml]

Linking an independently reported issue on this topic:

https://bugs.chromium.org/p/pdfium/issues/detail?id=1947

On Thursday, October 13, 2022 at 7:45:04 PM UTC+2 geisserml wrote:

Do PDFium developers have any comments on this?

[geisserml]

Getting back to this, this commit/patch from android's branch of pdfium seems related:
https://android.googlesource.com/platform/external/pdfium/+/8a5b0525467050ce19c01822cc2d785df946c084%5E%21
The linked issue is non-public at this time, though.

[Lei Zhang]

Filed crbug.com/413572037

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