imageproc mllama refactor (#7537)

Refactor mllama image processing code, and add pixtral and qwen2vl

model/pixtral/imageproc.go

@@ -0,0 +1,68 @@
+package pixtral
+
+import (
+	"fmt"
+	"image"
+	_ "image/jpeg"
+	_ "image/png"
+	"io"
+	"math"
+
+	"github.com/ollama/ollama/model/imageproc"
+)
+
+func getNumImageTokens(imageSize, patchSize image.Point) image.Point {
+	return image.Point{
+		(imageSize.X-1)/patchSize.X + 1,
+		(imageSize.Y-1)/patchSize.Y + 1,
+	}
+}
+
+func getResizeOutputImageSize(img image.Image, longestEdge int, patchSize image.Point) image.Point {
+	b := img.Bounds()
+	le := float64(longestEdge)
+	ratio := math.Max(float64(b.Max.Y)/le, float64(b.Max.X)/le)
+
+	newSize := img.Bounds().Max
+
+	if ratio > 1.0 {
+		newSize = image.Point{
+			int(math.Ceil(float64(b.Max.X) / ratio)),
+			int(math.Ceil(float64(b.Max.Y) / ratio)),
+		}
+	}
+
+	tokens := getNumImageTokens(newSize, patchSize)
+	return image.Point{
+		tokens.X * patchSize.X,
+		tokens.Y * patchSize.Y,
+	}
+}
+
+func resizeImage(img image.Image, format string, longestEdge int, patchSize image.Point) image.Image {
+	if format == "png" {
+		img = imageproc.Composite(img)
+	}
+
+	newSize := getResizeOutputImageSize(img, longestEdge, patchSize)
+
+	// todo should be ResizeBicubic, but it doesn't exist
+	return imageproc.Resize(img, newSize, imageproc.ResizeBilinear)
+}
+
+func Preprocess(imageData io.Reader) ([]float32, map[string]any, error) {
+	img, format, err := image.Decode(imageData)
+	if err != nil {
+		return nil, nil, fmt.Errorf("failed to decode image: %w", err)
+	}
+
+	longestEdge := 1024
+	patchSize := image.Point{16, 16}
+
+	img = resizeImage(img, format, longestEdge, patchSize)
+
+	data := imageproc.Normalize(img, imageproc.ClipDefaultMean, imageproc.ClipDefaultSTD, true, true)
+
+	opts := map[string]any{}
+	return data, opts, nil
+}