Module image 

Image and image-mask rendering — replaces Splash::fillImageMask, Splash::drawImage, and the four scaleImage* / scaleMask* helpers.

Scope

Only axis-aligned scaling (matrix[1] == 0 && matrix[2] == 0) with optional vertical flip (negative Y scale) is implemented. Rotated or skewed transforms return ImageResult::ArbitraryTransformSkipped so the caller can fall back to a general path.

Scaling strategy

Four Bresenham variants mirror the C++ scaleMask* / scaleImage* family:

Y axis	X axis	Method
down ↓	down ↓	Box-filter (average) in both axes
down ↓	up ↑	Box-filter in Y, nearest-neighbour in X
up ↑	down ↓	Nearest-neighbour in Y, box-filter in X
up ↑	up ↑	Nearest-neighbour in both axes

All four variants process source rows exactly once, allocating no extra heap per row. “Down” means scaled < src; “up” means scaled ≥ src.

Pixel-count contract

draw_image derives the component count directly from P::BYTES, eliminating any possibility of a caller passing a mismatched value.

C++ equivalents

• Splash::fillImageMask
• Splash::drawImage
• Splash::scaleMask{YdownXdown,YdownXup,YupXdown,YupXup}
• Splash::scaleImage{YdownXdown,YdownXup,YupXdown,YupXup}
• Splash::blitMask

Enums

ImageResult

Return value from fill_image_mask and draw_image.

Traits

ImageSource

Caller-supplied source for a colour image: one row at a time.

MaskSource

Caller-supplied source for a 1-bit image mask: one row at a time.

Functions

draw_image

Render a colour image with transformation.

fill_image_mask

Fill a 1-bit image mask using the current fill pattern.